diff --git a/src/blockchain_db/berkeleydb/db_bdb.cpp b/src/blockchain_db/berkeleydb/db_bdb.cpp
index a990d7aa..2a9e9a7f 100644
--- a/src/blockchain_db/berkeleydb/db_bdb.cpp
+++ b/src/blockchain_db/berkeleydb/db_bdb.cpp
@@ -118,6 +118,9 @@ const char* const BDB_OUTPUT_KEYS = "output_keys";
 
 const char* const BDB_SPENT_KEYS = "spent_keys";
 
+const char* const BDB_HF_STARTING_HEIGHTS = "hf_starting_heights";
+const char* const BDB_HF_VERSIONS = "hf_versions";
+
 const unsigned int MB = 1024 * 1024;
 // ND: FIXME: db keeps running out of locks when doing full syncs. Possible bug??? Set it to 5K for now.
 const unsigned int DB_MAX_LOCKS = 5000;
@@ -667,6 +670,9 @@ void BlockchainBDB::open(const std::string& filename, const int db_flags)
 
         m_spent_keys = new Db(m_env, 0);
 
+        m_hf_starting_heights = new Db(m_env, 0);
+        m_hf_versions = new Db(m_env, 0);
+
         // Tell DB about Dbs that need duplicate support
         // Note: no need to tell about sorting,
         //   as the default is insertion order, which we want
@@ -684,6 +690,9 @@ void BlockchainBDB::open(const std::string& filename, const int db_flags)
         m_output_indices->set_re_len(sizeof(uint64_t));
         m_output_keys->set_re_len(sizeof(output_data_t));
 
+        m_hf_starting_heights->set_re_len(sizeof(uint64_t));
+        m_hf_versions->set_re_len(sizeof(uint8_t));
+
         //TODO: Find out if we need to do Db::set_flags(DB_RENUMBER)
         //      for the RECNO databases.  We shouldn't as we're only
         //      inserting/removing from the end, but we'll see.
@@ -713,6 +722,9 @@ void BlockchainBDB::open(const std::string& filename, const int db_flags)
 
         m_spent_keys->open(txn, BDB_SPENT_KEYS, NULL, DB_HASH, DB_CREATE, 0);
 
+        m_hf_starting_heights->open(txn, BDB_HF_STARTING_HEIGHTS, NULL, DB_RECNO, DB_CREATE, 0);
+        m_hf_versions->open(txn, BDB_HF_VERSIONS, NULL, DB_RECNO, DB_CREATE, 0);
+
         txn.commit();
 
         DB_BTREE_STAT* stats;
@@ -785,6 +797,9 @@ void BlockchainBDB::sync()
         m_output_keys->sync(0);
 
         m_spent_keys->sync(0);
+
+        m_hf_starting_heights->sync(0);
+        m_hf_versions->sync(0);
     }
     catch (const std::exception& e)
     {
@@ -859,6 +874,12 @@ std::vector<std::string> BlockchainBDB::get_filenames() const
     m_spent_keys->get_dbname(pfname, pdbname);
     filenames.push_back(fname);
 
+    m_hf_starting_heights->get_dbname(pfname, pdbname);
+    filenames.push_back(fname);
+
+    m_hf_versions->get_dbname(pfname, pdbname);
+    filenames.push_back(fname);
+
     std::vector<std::string> full_paths;
 
     for (auto& filename : filenames)
@@ -1839,6 +1860,60 @@ void BlockchainBDB::get_output_tx_and_index(const uint64_t& amount, const std::v
     LOG_PRINT_L3("db3: " << db3);
 }
 
+void BlockchainBDB::set_hard_fork_starting_height(uint8_t version, uint64_t height)
+{
+    LOG_PRINT_L3("BlockchainBDB::" << __func__);
+    check_open();
+
+    Dbt_copy<uint8_t> val_key(version);
+    Dbt_copy<uint64_t> val(height);
+    if (m_hf_starting_heights->put(DB_DEFAULT_TX, &val_key, &val, 0))
+        throw1(DB_ERROR("Error adding hard fork starting height to db transaction."));
+}
+
+uint64_t BlockchainBDB::get_hard_fork_starting_height(uint8_t version) const
+{
+    LOG_PRINT_L3("BlockchainBDB::" << __func__);
+    check_open();
+
+    Dbt_copy<uint8_t> key(version);
+    Dbt_copy<uint64_t> result;
+
+    auto get_result = m_hf_starting_heights->get(DB_DEFAULT_TX, &key, &result, 0);
+    if (get_result == DB_NOTFOUND)
+        return std::numeric_limits<uint64_t>::max();
+    else if (get_result)
+        throw0(DB_ERROR("Error attempting to retrieve hard fork starting height from the db"));
+
+    return result;
+}
+
+void BlockchainBDB::set_hard_fork_version(uint64_t height, uint8_t version)
+{
+    LOG_PRINT_L3("BlockchainBDB::" << __func__);
+    check_open();
+
+    Dbt_copy<uint64_t> val_key(height);
+    Dbt_copy<uint8_t> val(version);
+    if (m_hf_versions->put(DB_DEFAULT_TX, &val_key, &val, 0))
+        throw1(DB_ERROR("Error adding hard fork version to db transaction."));
+}
+
+uint8_t BlockchainBDB::get_hard_fork_version(uint64_t height) const
+{
+    LOG_PRINT_L3("BlockchainBDB::" << __func__);
+    check_open();
+
+    Dbt_copy<uint64_t> key(height);
+    Dbt_copy<uint8_t> result;
+
+    auto get_result = m_hf_versions->get(DB_DEFAULT_TX, &key, &result, 0);
+    if (get_result == DB_NOTFOUND || get_result)
+        throw0(DB_ERROR("Error attempting to retrieve hard fork version from the db"));
+
+    return result;
+}
+
 void BlockchainBDB::checkpoint_worker() const
 {
     LOG_PRINT_L0("Entering BDB checkpoint thread.")
diff --git a/src/blockchain_db/berkeleydb/db_bdb.h b/src/blockchain_db/berkeleydb/db_bdb.h
index f92bbef6..54edcf0a 100644
--- a/src/blockchain_db/berkeleydb/db_bdb.h
+++ b/src/blockchain_db/berkeleydb/db_bdb.h
@@ -374,6 +374,13 @@ private:
   virtual void remove_spent_key(const crypto::key_image& k_image);
 
   void get_output_global_indices(const uint64_t& amount, const std::vector<uint64_t> &offsets, std::vector<uint64_t> &global_indices);
+
+  // Hard fork related storage
+  virtual void set_hard_fork_starting_height(uint8_t version, uint64_t height);
+  virtual uint64_t get_hard_fork_starting_height(uint8_t version) const;
+  virtual void set_hard_fork_version(uint64_t height, uint8_t version);
+  virtual uint8_t get_hard_fork_version(uint64_t height) const;
+
   /**
    * @brief convert a tx output to a blob for storage
    *
@@ -430,6 +437,9 @@ private:
 
   Db* m_spent_keys;
 
+  Db* m_hf_starting_heights;
+  Db* m_hf_versions;
+
   uint64_t m_height;
   uint64_t m_num_outputs;
   std::string m_folder;
diff --git a/src/blockchain_db/blockchain_db.h b/src/blockchain_db/blockchain_db.h
index 25a34fc0..24bf4024 100644
--- a/src/blockchain_db/blockchain_db.h
+++ b/src/blockchain_db/blockchain_db.h
@@ -493,6 +493,12 @@ public:
   // returns true if key image <img> is present in spent key images storage
   virtual bool has_key_image(const crypto::key_image& img) const = 0;
 
+  // Hard fork related storage
+  virtual void set_hard_fork_starting_height(uint8_t version, uint64_t height) = 0;
+  virtual uint64_t get_hard_fork_starting_height(uint8_t version) const = 0;
+  virtual void set_hard_fork_version(uint64_t height, uint8_t version) = 0;
+  virtual uint8_t get_hard_fork_version(uint64_t height) const = 0;
+
   void set_auto_remove_logs(bool auto_remove) { m_auto_remove_logs = auto_remove; }
 
   bool m_open;
diff --git a/src/blockchain_db/lmdb/db_lmdb.cpp b/src/blockchain_db/lmdb/db_lmdb.cpp
index 1583a0c0..2695d83f 100644
--- a/src/blockchain_db/lmdb/db_lmdb.cpp
+++ b/src/blockchain_db/lmdb/db_lmdb.cpp
@@ -131,6 +131,15 @@ auto compare_uint64 = [](const MDB_val *a, const MDB_val *b)
   else return 1;
 };
 
+auto compare_uint8 = [](const MDB_val *a, const MDB_val *b)
+{
+  const uint8_t va = *(const uint8_t*)a->mv_data;
+  const uint8_t vb = *(const uint8_t*)b->mv_data;
+  if (va < vb) return -1;
+  else if (va == vb) return 0;
+  else return 1;
+};
+
 int compare_hash32(const MDB_val *a, const MDB_val *b)
 {
 	uint32_t *va = (uint32_t*) a->mv_data;
@@ -166,6 +175,9 @@ const char* const LMDB_OUTPUTS = "outputs";
 const char* const LMDB_OUTPUT_GINDICES = "output_gindices";
 const char* const LMDB_SPENT_KEYS = "spent_keys";
 
+const char* const LMDB_HF_STARTING_HEIGHTS = "hf_starting_heights";
+const char* const LMDB_HF_VERSIONS = "hf_versions";
+
 inline void lmdb_db_open(MDB_txn* txn, const char* name, int flags, MDB_dbi& dbi, const std::string& error_string)
 {
   if (mdb_dbi_open(txn, name, flags, &dbi))
@@ -1022,6 +1034,9 @@ void BlockchainLMDB::open(const std::string& filename, const int mdb_flags)
 
   lmdb_db_open(txn, LMDB_SPENT_KEYS, MDB_CREATE, m_spent_keys, "Failed to open db handle for m_spent_keys");
 
+  lmdb_db_open(txn, LMDB_HF_STARTING_HEIGHTS, MDB_CREATE, m_hf_starting_heights, "Failed to open db handle for m_hf_starting_heights");
+  lmdb_db_open(txn, LMDB_HF_VERSIONS, MDB_CREATE, m_hf_versions, "Failed to open db handle for m_hf_versions");
+
   mdb_set_dupsort(txn, m_output_amounts, compare_uint64);
   mdb_set_dupsort(txn, m_tx_outputs, compare_uint64);
   mdb_set_compare(txn, m_spent_keys, compare_hash32);
@@ -1029,6 +1044,8 @@ void BlockchainLMDB::open(const std::string& filename, const int mdb_flags)
   mdb_set_compare(txn, m_txs, compare_hash32);
   mdb_set_compare(txn, m_tx_unlocks, compare_hash32);
   mdb_set_compare(txn, m_tx_heights, compare_hash32);
+  mdb_set_compare(txn, m_hf_starting_heights, compare_uint8);
+  mdb_set_compare(txn, m_hf_versions, compare_uint64);
 
   // get and keep current height
   MDB_stat db_stats;
@@ -2347,4 +2364,111 @@ void BlockchainLMDB::get_output_tx_and_index(const uint64_t& amount, const std::
 	LOG_PRINT_L3("db3: " << db3);
 }
 
+void BlockchainLMDB::set_hard_fork_starting_height(uint8_t version, uint64_t height)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  mdb_txn_safe txn;
+  mdb_txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, 0, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+    txn_ptr = &txn;
+  }
+
+  MDB_val_copy<uint8_t> val_key(version);
+  MDB_val_copy<uint64_t> val_value(height);
+  if (auto result = mdb_put(*txn_ptr, m_hf_starting_heights, &val_key, &val_value, 0))
+    throw1(DB_ERROR(std::string("Error adding hard fork starting height to db transaction: ").append(mdb_strerror(result)).c_str()));
+
+  if (!m_batch_active)
+    txn.commit();
+}
+
+uint64_t BlockchainLMDB::get_hard_fork_starting_height(uint8_t version) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  mdb_txn_safe txn;
+  mdb_txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+    txn_ptr = &txn;
+  }
+
+  MDB_val_copy<uint8_t> val_key(version);
+  MDB_val val_ret;
+  auto result = mdb_get(*txn_ptr, m_hf_starting_heights, &val_key, &val_ret);
+  if (result == MDB_NOTFOUND)
+    return std::numeric_limits<uint64_t>::max();
+  if (result)
+    throw0(DB_ERROR("Error attempting to retrieve a hard fork starting height from the db"));
+
+  if (!m_batch_active)
+    txn.commit();
+  return *(const uint64_t*)val_ret.mv_data;
+}
+
+void BlockchainLMDB::set_hard_fork_version(uint64_t height, uint8_t version)
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+//LOG_PRINT_L1("BlockchainLMDB::set_hard_fork_version: batch " << m_batch_active << ", height " << height << ", version " << (int)version);
+  mdb_txn_safe txn;
+  mdb_txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, 0, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+    txn_ptr = &txn;
+  }
+
+  MDB_val_copy<uint64_t> val_key(height);
+  MDB_val_copy<uint8_t> val_value(version);
+  if (auto result = mdb_put(*txn_ptr, m_hf_versions, &val_key, &val_value, 0))
+    throw1(DB_ERROR(std::string("Error adding hard fork version to db transaction: ").append(mdb_strerror(result)).c_str()));
+
+  if (!m_batch_active)
+    txn.commit();
+}
+
+uint8_t BlockchainLMDB::get_hard_fork_version(uint64_t height) const
+{
+  LOG_PRINT_L3("BlockchainLMDB::" << __func__);
+  check_open();
+
+  mdb_txn_safe txn;
+  mdb_txn_safe* txn_ptr = &txn;
+  if (m_batch_active)
+    txn_ptr = m_write_txn;
+  else
+  {
+    if (mdb_txn_begin(m_env, NULL, MDB_RDONLY, txn))
+      throw0(DB_ERROR("Failed to create a transaction for the db"));
+    txn_ptr = &txn;
+  }
+
+  MDB_val_copy<uint64_t> val_key(height);
+  MDB_val val_ret;
+  auto result = mdb_get(*txn_ptr, m_hf_versions, &val_key, &val_ret);
+  if (result == MDB_NOTFOUND || result)
+    throw0(DB_ERROR("Error attempting to retrieve a hard fork version from the db"));
+
+  if (!m_batch_active)
+    txn.commit();
+  return *(const uint8_t*)val_ret.mv_data;
+}
+
 }  // namespace cryptonote
diff --git a/src/blockchain_db/lmdb/db_lmdb.h b/src/blockchain_db/lmdb/db_lmdb.h
index b4c19780..38095429 100644
--- a/src/blockchain_db/lmdb/db_lmdb.h
+++ b/src/blockchain_db/lmdb/db_lmdb.h
@@ -238,6 +238,12 @@ private:
 
   virtual void remove_spent_key(const crypto::key_image& k_image);
 
+  // Hard fork
+  virtual void set_hard_fork_starting_height(uint8_t version, uint64_t height);
+  virtual uint64_t get_hard_fork_starting_height(uint8_t version) const;
+  virtual void set_hard_fork_version(uint64_t height, uint8_t version);
+  virtual uint8_t get_hard_fork_version(uint64_t height) const;
+
   /**
    * @brief convert a tx output to a blob for storage
    *
@@ -292,6 +298,9 @@ private:
 
   MDB_dbi m_spent_keys;
 
+  MDB_dbi m_hf_starting_heights;
+  MDB_dbi m_hf_versions;
+
   uint64_t m_height;
   uint64_t m_num_outputs;
   std::string m_folder;
diff --git a/src/cryptonote_core/CMakeLists.txt b/src/cryptonote_core/CMakeLists.txt
index 6315fc4f..7b0a5017 100644
--- a/src/cryptonote_core/CMakeLists.txt
+++ b/src/cryptonote_core/CMakeLists.txt
@@ -37,7 +37,8 @@ set(cryptonote_core_sources
   cryptonote_format_utils.cpp
   difficulty.cpp
   miner.cpp
-  tx_pool.cpp)
+  tx_pool.cpp
+  hardfork.cpp)
 
 set(cryptonote_core_headers)
 
@@ -60,7 +61,8 @@ set(cryptonote_core_private_headers
   miner.h
   tx_extra.h
   tx_pool.h
-  verification_context.h)
+  verification_context.h
+  hardfork.h)
 
 if(PER_BLOCK_CHECKPOINT)
 	set(Blocks "blocks")
diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index 09f8f8d7..65d07dcf 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -69,6 +69,18 @@ extern "C" void slow_hash_free_state();
 
 DISABLE_VS_WARNINGS(4267)
 
+static const struct {
+  uint8_t version;
+  uint64_t height;
+  time_t time;
+} hard_forks[] = {
+  // version 1 from the start of the blockchain
+  { 1, 1, 1341378000 },
+
+  // version 2 can start from block 1009827, setup on the 20th of september
+  { 2, 1009827, 1442763710 },
+};
+
 //------------------------------------------------------------------
 Blockchain::Blockchain(tx_memory_pool& tx_pool) :
 m_db(), m_tx_pool(tx_pool), m_timestamps_and_difficulties_height(0), m_current_block_cumul_sz_limit(0), m_is_in_checkpoint_zone(false), 
@@ -118,6 +130,11 @@ void Blockchain::serialize(archive_t & ar, const unsigned int version)
         }
     }
 
+    if (version > 12)
+    {
+        ar & *m_hardfork;
+    }
+
     LOG_PRINT_L3("Blockchain storage:" << std::endl << "m_blocks: " << m_db->height() << std::endl << "m_blocks_index: " << m_blocks_index.size() << std::endl << "m_transactions: " << m_transactions.size() << std::endl << "dummy_key_images_container: " << dummy_key_images_container.size() << std::endl << "m_alternative_chains: " << m_alternative_chains.size() << std::endl << "m_outputs: " << m_outputs.size() << std::endl << "m_invalid_blocks: " << m_invalid_blocks.size() << std::endl << "m_current_block_cumul_sz_limit: " << m_current_block_cumul_sz_limit);
 }
 //------------------------------------------------------------------
@@ -270,6 +287,11 @@ bool Blockchain::init(BlockchainDB* db, const bool testnet)
 
     m_db = db;
 
+    m_hardfork = new HardFork(*db);
+    for (size_t n = 0; n < sizeof(hard_forks) / sizeof(hard_forks[0]); ++n)
+      m_hardfork->add(hard_forks[n].version, hard_forks[n].height, hard_forks[n].time);
+    m_hardfork->init();
+
     // if the blockchain is new, add the genesis block
     // this feels kinda kludgy to do it this way, but can be looked at later.
     // TODO: add function to create and store genesis block,
@@ -416,6 +438,7 @@ bool Blockchain::deinit()
         LOG_PRINT_L0("There was an issue closing/storing the blockchain, shutting down now to prevent issues!");
     }
 
+    delete m_hardfork;
     delete m_db;
     return true;
 }
@@ -706,6 +729,8 @@ bool Blockchain::rollback_blockchain_switching(std::list<block>& original_chain,
         CHECK_AND_ASSERT_MES(r && bvc.m_added_to_main_chain, false, "PANIC! failed to add (again) block while chain switching during the rollback!");
     }
 
+    m_hardfork->reorganize_from_chain_height(rollback_height);
+
     LOG_PRINT_L1("Rollback to height " << rollback_height << " was successful.");
     if (original_chain.size())
     {
@@ -803,6 +828,8 @@ bool Blockchain::switch_to_alternative_blockchain(std::list<blocks_ext_by_hash::
         m_alternative_chains.erase(ch_ent);
     }
 
+    m_hardfork->reorganize_from_chain_height(split_height);
+
     LOG_PRINT_GREEN("REORGANIZE SUCCESS! on height: " << split_height << ", new blockchain size: " << m_db->height(), LOG_LEVEL_0);
     return true;
 }
@@ -972,12 +999,13 @@ bool Blockchain::create_block_template(block& b, const account_public_address& m
     uint64_t already_generated_coins;
 
     CRITICAL_REGION_BEGIN(m_blockchain_lock);
-    b.major_version = CURRENT_BLOCK_MAJOR_VERSION;
-    b.minor_version = CURRENT_BLOCK_MINOR_VERSION;
+    height = m_db->height();
+
+    b.major_version = m_hardfork->get_ideal_version();
+    b.minor_version = 0;
     b.prev_id = get_tail_id();
     b.timestamp = time(NULL);
 
-    height = m_db->height();
     diffic = get_difficulty_for_next_block();
     CHECK_AND_ASSERT_MES(diffic, false, "difficulty owverhead.");
 
@@ -1622,7 +1650,7 @@ bool Blockchain::get_transactions(const t_ids_container& txs_ids, t_tx_container
     return true;
 }
 //------------------------------------------------------------------
-void Blockchain::print_blockchain(uint64_t start_index, uint64_t end_index)
+void Blockchain::print_blockchain(uint64_t start_index, uint64_t end_index) const
 {
     LOG_PRINT_L3("Blockchain::" << __func__);
     std::stringstream ss;
@@ -1642,7 +1670,7 @@ void Blockchain::print_blockchain(uint64_t start_index, uint64_t end_index)
     LOG_PRINT_L0("Blockchain printed with log level 1");
 }
 //------------------------------------------------------------------
-void Blockchain::print_blockchain_index()
+void Blockchain::print_blockchain_index() const
 {
     LOG_PRINT_L3("Blockchain::" << __func__);
     std::stringstream ss;
@@ -1660,7 +1688,7 @@ void Blockchain::print_blockchain_index()
 }
 //------------------------------------------------------------------
 //TODO: remove this function and references to it
-void Blockchain::print_blockchain_outs(const std::string& file)
+void Blockchain::print_blockchain_outs(const std::string& file) const
 {
     LOG_PRINT_L3("Blockchain::" << __func__);
     return;
@@ -2245,6 +2273,13 @@ bool Blockchain::handle_block_to_main_chain(const block& bl, const crypto::hash&
     CRITICAL_REGION_LOCAL(m_blockchain_lock);
     TIME_MEASURE_START(t1);
 
+    // this is a cheap test
+    if (!m_hardfork->check(bl))
+    {
+        LOG_PRINT_L1("Block with id: " << id << std::endl << "has old version: " << bl.major_version << std::endl << "current: " << m_hardfork->get_current_version());
+        return false;
+    }
+
     if(bl.prev_id != get_tail_id())
     {
         LOG_PRINT_L1("Block with id: " << id << std::endl << "has wrong prev_id: " << bl.prev_id << std::endl << "expected: " << get_tail_id());
@@ -2521,6 +2556,9 @@ bool Blockchain::handle_block_to_main_chain(const block& bl, const crypto::hash&
 
     update_next_cumulative_size_limit();
 
+    // this will not fail since check succeeded above
+    m_hardfork->add(bl, new_height - 1);
+
     LOG_PRINT_L1("+++++ BLOCK SUCCESSFULLY ADDED" << std::endl << "id:\t" << id << std::endl << "PoW:\t" << proof_of_work << std::endl << "HEIGHT " << new_height << ", difficulty:\t" << current_diffic << std::endl << "block reward: " << print_money(fee_summary + base_reward) << "(" << print_money(base_reward) << " + " << print_money(fee_summary) << "), coinbase_blob_size: " << coinbase_blob_size << ", cumulative size: " << cumulative_block_size << ", " << block_processing_time << "(" << target_calculating_time << "/" << longhash_calculating_time << ")ms");
     if(m_show_time_stats)
     {
@@ -3054,3 +3092,13 @@ void Blockchain::set_user_options(uint64_t maxthreads, uint64_t blocks_per_sync,
     m_db_blocks_per_sync = blocks_per_sync;
     m_max_prepare_blocks_threads = maxthreads;
 }
+
+HardFork::State Blockchain::get_hard_fork_state() const
+{
+    return m_hardfork->get_state();
+}
+
+bool Blockchain::get_hard_fork_voting_info(uint8_t version, uint32_t &window, uint32_t &votes, uint32_t &threshold, uint8_t &voting) const
+{
+    return m_hardfork->get_voting_info(version, window, votes, threshold, voting);
+}
diff --git a/src/cryptonote_core/blockchain.h b/src/cryptonote_core/blockchain.h
index 57763f6c..a248682f 100644
--- a/src/cryptonote_core/blockchain.h
+++ b/src/cryptonote_core/blockchain.h
@@ -38,6 +38,8 @@
 #include <boost/multi_index/member.hpp>
 #include <boost/foreach.hpp>
 #include <atomic>
+#include <unordered_map>
+#include <unordered_set>
 
 #include "syncobj.h"
 #include "string_tools.h"
@@ -50,6 +52,7 @@
 #include "verification_context.h"
 #include "crypto/hash.h"
 #include "checkpoints.h"
+#include "hardfork.h"
 #include "blockchain_db/blockchain_db.h"
 
 namespace cryptonote
@@ -142,9 +145,9 @@ namespace cryptonote
     bool get_transactions(const t_ids_container& txs_ids, t_tx_container& txs, t_missed_container& missed_txs) const;
 
     //debug functions
-    void print_blockchain(uint64_t start_index, uint64_t end_index);
-    void print_blockchain_index();
-    void print_blockchain_outs(const std::string& file);
+    void print_blockchain(uint64_t start_index, uint64_t end_index) const;
+    void print_blockchain_index() const;
+    void print_blockchain_outs(const std::string& file) const;
 
     void check_against_checkpoints(const checkpoints& points, bool enforce);
     void set_enforce_dns_checkpoints(bool enforce);
@@ -156,6 +159,11 @@ namespace cryptonote
 
     void set_show_time_stats(bool stats) { m_show_time_stats = stats; }
     
+    HardFork::State get_hard_fork_state() const;
+    uint8_t get_current_hard_fork_version() const { return m_hardfork->get_current_version(); }
+    uint8_t get_ideal_hard_fork_version() const { return m_hardfork->get_ideal_version(); }
+    bool get_hard_fork_voting_info(uint8_t version, uint32_t &window, uint32_t &votes, uint32_t &threshold, uint8_t &voting) const;
+
     BlockchainDB& get_db()
     {
       return *m_db;
@@ -225,6 +233,8 @@ namespace cryptonote
     std::atomic<bool> m_is_blockchain_storing;
     bool m_enforce_dns_checkpoints;
 
+    HardFork *m_hardfork;
+
     template<class visitor_t>
     inline bool scan_outputkeys_for_indexes(const txin_to_key& tx_in_to_key, visitor_t &vis, const crypto::hash &tx_prefix_hash, uint64_t* pmax_related_block_height = NULL) const;
     bool check_tx_input(const txin_to_key& txin, const crypto::hash& tx_prefix_hash, const std::vector<crypto::signature>& sig, std::vector<crypto::public_key> &output_keys, uint64_t* pmax_related_block_height);
@@ -266,10 +276,10 @@ namespace cryptonote
   /*                                                                      */
   /************************************************************************/
 
-  #define CURRENT_BLOCKCHAIN_STORAGE_ARCHIVE_VER    12
+  #define CURRENT_BLOCKCHAIN_ARCHIVE_VER    13
 
   //------------------------------------------------------------------
 
 }  // namespace cryptonote
 
-BOOST_CLASS_VERSION(cryptonote::Blockchain, CURRENT_BLOCKCHAIN_STORAGE_ARCHIVE_VER)
+BOOST_CLASS_VERSION(cryptonote::Blockchain, CURRENT_BLOCKCHAIN_ARCHIVE_VER)
diff --git a/src/cryptonote_core/blockchain_storage.cpp b/src/cryptonote_core/blockchain_storage.cpp
index ee426368..4a4d348b 100644
--- a/src/cryptonote_core/blockchain_storage.cpp
+++ b/src/cryptonote_core/blockchain_storage.cpp
@@ -1178,7 +1178,7 @@ double blockchain_storage::get_avg_block_size( size_t count) const
 		return average;
 }
 //------------------------------------------------------------------
-void blockchain_storage::print_blockchain(uint64_t start_index, uint64_t end_index)
+void blockchain_storage::print_blockchain(uint64_t start_index, uint64_t end_index) const
 {
   std::stringstream ss;
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
@@ -1198,7 +1198,7 @@ void blockchain_storage::print_blockchain(uint64_t start_index, uint64_t end_ind
   LOG_PRINT_L0("Blockchain printed with log level 1");
 }
 //------------------------------------------------------------------
-void blockchain_storage::print_blockchain_index()
+void blockchain_storage::print_blockchain_index() const
 {
   std::stringstream ss;
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
@@ -1208,7 +1208,7 @@ void blockchain_storage::print_blockchain_index()
   LOG_PRINT_L0("Current blockchain index:" << ENDL << ss.str());
 }
 //------------------------------------------------------------------
-void blockchain_storage::print_blockchain_outs(const std::string& file)
+void blockchain_storage::print_blockchain_outs(const std::string& file) const
 {
   std::stringstream ss;
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
diff --git a/src/cryptonote_core/blockchain_storage.h b/src/cryptonote_core/blockchain_storage.h
index aeeef31b..2a4cfcd4 100644
--- a/src/cryptonote_core/blockchain_storage.h
+++ b/src/cryptonote_core/blockchain_storage.h
@@ -173,9 +173,9 @@ namespace cryptonote
       return true;
     }
     //debug functions
-    void print_blockchain(uint64_t start_index, uint64_t end_index);
-    void print_blockchain_index();
-    void print_blockchain_outs(const std::string& file);
+    void print_blockchain(uint64_t start_index, uint64_t end_index) const;
+    void print_blockchain_index() const;
+    void print_blockchain_outs(const std::string& file) const;
     void check_against_checkpoints(const checkpoints& points, bool enforce);
     bool update_checkpoints(const std::string& file_path, bool check_dns);
     void set_enforce_dns_checkpoints(bool enforce_checkpoints);
diff --git a/src/cryptonote_core/cryptonote_basic.h b/src/cryptonote_core/cryptonote_basic.h
index 07745bf0..d3db5006 100644
--- a/src/cryptonote_core/cryptonote_basic.h
+++ b/src/cryptonote_core/cryptonote_basic.h
@@ -182,7 +182,6 @@ namespace cryptonote
       FIELD(extra)
     END_SERIALIZE()
 
-
   protected:
     transaction_prefix(){}
   };
@@ -278,7 +277,7 @@ namespace cryptonote
   /************************************************************************/
   struct block_header
   {
-    uint8_t major_version;
+    uint8_t major_version;  // now used as a voting mechanism, rather than how this particular block is built
     uint8_t minor_version;
     uint64_t timestamp;
     crypto::hash  prev_id;
@@ -286,7 +285,6 @@ namespace cryptonote
 
     BEGIN_SERIALIZE()
       VARINT_FIELD(major_version)
-      if(major_version > CURRENT_BLOCK_MAJOR_VERSION) return false;
       VARINT_FIELD(minor_version)
       VARINT_FIELD(timestamp)
       FIELD(prev_id)
diff --git a/src/cryptonote_core/cryptonote_core.cpp b/src/cryptonote_core/cryptonote_core.cpp
index 4d90eec1..4ade50cd 100644
--- a/src/cryptonote_core/cryptonote_core.cpp
+++ b/src/cryptonote_core/cryptonote_core.cpp
@@ -168,37 +168,37 @@ namespace cryptonote
     return true;
   }
   //-----------------------------------------------------------------------------------------------
-  uint64_t core::get_current_blockchain_height()
+  uint64_t core::get_current_blockchain_height() const
   {
     return m_blockchain_storage.get_current_blockchain_height();
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_blockchain_top(uint64_t& height, crypto::hash& top_id)
+  bool core::get_blockchain_top(uint64_t& height, crypto::hash& top_id) const
   {
     top_id = m_blockchain_storage.get_tail_id(height);
     return true;
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks, std::list<transaction>& txs)
+  bool core::get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks, std::list<transaction>& txs) const
   {
     return m_blockchain_storage.get_blocks(start_offset, count, blocks, txs);
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks)
+  bool core::get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks) const
   {
     return m_blockchain_storage.get_blocks(start_offset, count, blocks);
   }  //-----------------------------------------------------------------------------------------------
-  bool core::get_transactions(const std::vector<crypto::hash>& txs_ids, std::list<transaction>& txs, std::list<crypto::hash>& missed_txs)
+  bool core::get_transactions(const std::vector<crypto::hash>& txs_ids, std::list<transaction>& txs, std::list<crypto::hash>& missed_txs) const
   {
     return m_blockchain_storage.get_transactions(txs_ids, txs, missed_txs);
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_alternative_blocks(std::list<block>& blocks)
+  bool core::get_alternative_blocks(std::list<block>& blocks) const
   {
     return m_blockchain_storage.get_alternative_blocks(blocks);
   }
   //-----------------------------------------------------------------------------------------------
-  size_t core::get_alternative_blocks_count()
+  size_t core::get_alternative_blocks_count() const
   {
     return m_blockchain_storage.get_alternative_blocks_count();
   }
@@ -385,12 +385,12 @@ namespace cryptonote
 	  m_test_drop_download_height = height;
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_test_drop_download()
+  bool core::get_test_drop_download() const
   {
 	  return m_test_drop_download;
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_test_drop_download_height()
+  bool core::get_test_drop_download_height() const
   {
 	  if (m_test_drop_download_height == 0)
 		return true;
@@ -451,7 +451,7 @@ namespace cryptonote
     return r;
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_stat_info(core_stat_info& st_inf)
+  bool core::get_stat_info(core_stat_info& st_inf) const
   {
     st_inf.mining_speed = m_miner.get_speed();
     st_inf.alternative_blocks = m_blockchain_storage.get_alternative_blocks_count();
@@ -462,7 +462,7 @@ namespace cryptonote
   }
 
   //-----------------------------------------------------------------------------------------------
-  bool core::check_tx_semantic(const transaction& tx, bool keeped_by_block)
+  bool core::check_tx_semantic(const transaction& tx, bool keeped_by_block) const
   {
     if(!tx.vin.size())
     {
@@ -515,12 +515,12 @@ namespace cryptonote
     return true;
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::is_key_image_spent(const crypto::key_image &key_image)
+  bool core::is_key_image_spent(const crypto::key_image &key_image) const
   {
     return m_blockchain_storage.have_tx_keyimg_as_spent(key_image);
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::are_key_images_spent(const std::vector<crypto::key_image>& key_im, std::vector<bool> &spent)
+  bool core::are_key_images_spent(const std::vector<crypto::key_image>& key_im, std::vector<bool> &spent) const
   {
     spent.clear();
     BOOST_FOREACH(auto& ki, key_im)
@@ -530,7 +530,7 @@ namespace cryptonote
     return true;
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::check_tx_inputs_keyimages_diff(const transaction& tx)
+  bool core::check_tx_inputs_keyimages_diff(const transaction& tx) const
   {
     std::unordered_set<crypto::key_image> ki;
     BOOST_FOREACH(const auto& in, tx.vin)
@@ -551,7 +551,7 @@ namespace cryptonote
     return add_new_tx(tx, tx_hash, tx_prefix_hash, bl.size(), tvc, keeped_by_block);
   }
   //-----------------------------------------------------------------------------------------------
-  size_t core::get_blockchain_total_transactions()
+  size_t core::get_blockchain_total_transactions() const
   {
     return m_blockchain_storage.get_total_transactions();
   }
@@ -583,22 +583,22 @@ namespace cryptonote
     return m_blockchain_storage.create_block_template(b, adr, diffic, height, ex_nonce);
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, NOTIFY_RESPONSE_CHAIN_ENTRY::request& resp)
+  bool core::find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, NOTIFY_RESPONSE_CHAIN_ENTRY::request& resp) const
   {
     return m_blockchain_storage.find_blockchain_supplement(qblock_ids, resp);
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::find_blockchain_supplement(const uint64_t req_start_block, const std::list<crypto::hash>& qblock_ids, std::list<std::pair<block, std::list<transaction> > >& blocks, uint64_t& total_height, uint64_t& start_height, size_t max_count)
+  bool core::find_blockchain_supplement(const uint64_t req_start_block, const std::list<crypto::hash>& qblock_ids, std::list<std::pair<block, std::list<transaction> > >& blocks, uint64_t& total_height, uint64_t& start_height, size_t max_count) const
   {
     return m_blockchain_storage.find_blockchain_supplement(req_start_block, qblock_ids, blocks, total_height, start_height, max_count);
   }
   //-----------------------------------------------------------------------------------------------
-  void core::print_blockchain(uint64_t start_index, uint64_t end_index)
+  void core::print_blockchain(uint64_t start_index, uint64_t end_index) const
   {
     m_blockchain_storage.print_blockchain(start_index, end_index);
   }
   //-----------------------------------------------------------------------------------------------
-  void core::print_blockchain_index()
+  void core::print_blockchain_index() const
   {
     m_blockchain_storage.print_blockchain_index();
   }
@@ -608,12 +608,12 @@ namespace cryptonote
     m_blockchain_storage.print_blockchain_outs(file);
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::request& req, COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::response& res)
+  bool core::get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::request& req, COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::response& res) const
   {
     return m_blockchain_storage.get_random_outs_for_amounts(req, res);
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_tx_outputs_gindexs(const crypto::hash& tx_id, std::vector<uint64_t>& indexs)
+  bool core::get_tx_outputs_gindexs(const crypto::hash& tx_id, std::vector<uint64_t>& indexs) const
   {
     return m_blockchain_storage.get_tx_outputs_gindexs(tx_id, indexs);
   }
@@ -728,7 +728,7 @@ namespace cryptonote
   //-----------------------------------------------------------------------------------------------
   // Used by the RPC server to check the size of an incoming
   // block_blob
-  bool core::check_incoming_block_size(const blobdata& block_blob)
+  bool core::check_incoming_block_size(const blobdata& block_blob) const
   {
     if(block_blob.size() > get_max_block_size())
     {
@@ -738,32 +738,32 @@ namespace cryptonote
     return true;
   }
   //-----------------------------------------------------------------------------------------------
-  crypto::hash core::get_tail_id()
+  crypto::hash core::get_tail_id() const
   {
     return m_blockchain_storage.get_tail_id();
   }
   //-----------------------------------------------------------------------------------------------
-  size_t core::get_pool_transactions_count()
+  size_t core::get_pool_transactions_count() const
   {
     return m_mempool.get_transactions_count();
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::have_block(const crypto::hash& id)
+  bool core::have_block(const crypto::hash& id) const
   {
     return m_blockchain_storage.have_block(id);
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::parse_tx_from_blob(transaction& tx, crypto::hash& tx_hash, crypto::hash& tx_prefix_hash, const blobdata& blob)
+  bool core::parse_tx_from_blob(transaction& tx, crypto::hash& tx_hash, crypto::hash& tx_prefix_hash, const blobdata& blob) const
   {
     return parse_and_validate_tx_from_blob(blob, tx, tx_hash, tx_prefix_hash);
   }
   //-----------------------------------------------------------------------------------------------
-    bool core::check_tx_syntax(const transaction& tx)
+  bool core::check_tx_syntax(const transaction& tx) const
   {
     return true;
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_pool_transactions(std::list<transaction>& txs)
+  bool core::get_pool_transactions(std::list<transaction>& txs) const
   {
     m_mempool.get_transactions(txs);
     return true;
@@ -774,7 +774,7 @@ namespace cryptonote
     return m_mempool.get_transactions_and_spent_keys_info(tx_infos, key_image_infos);
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_short_chain_history(std::list<crypto::hash>& ids)
+  bool core::get_short_chain_history(std::list<crypto::hash>& ids) const
   {
     return m_blockchain_storage.get_short_chain_history(ids);
   }
@@ -784,12 +784,12 @@ namespace cryptonote
     return m_blockchain_storage.handle_get_objects(arg, rsp);
   }
   //-----------------------------------------------------------------------------------------------
-  crypto::hash core::get_block_id_by_height(uint64_t height)
+  crypto::hash core::get_block_id_by_height(uint64_t height) const
   {
     return m_blockchain_storage.get_block_id_by_height(height);
   }
   //-----------------------------------------------------------------------------------------------
-  bool core::get_block_by_hash(const crypto::hash &h, block &blk)
+  bool core::get_block_by_hash(const crypto::hash &h, block &blk) const
   {
     return m_blockchain_storage.get_block_by_hash(h, blk);
   }
@@ -798,7 +798,7 @@ namespace cryptonote
   //  m_blockchain_storage.get_all_known_block_ids(main, alt, invalid);
   //}
   //-----------------------------------------------------------------------------------------------
-  std::string core::print_pool(bool short_format)
+  std::string core::print_pool(bool short_format) const
   {
     return m_mempool.print_pool(short_format);
   }
@@ -830,11 +830,37 @@ namespace cryptonote
 #else
     m_store_blockchain_interval.do_call(boost::bind(&blockchain_storage::store_blockchain, &m_blockchain_storage));
 #endif
+    m_fork_moaner.do_call(boost::bind(&core::check_fork_time, this));
     m_miner.on_idle();
     m_mempool.on_idle();
     return true;
   }
   //-----------------------------------------------------------------------------------------------
+  bool core::check_fork_time()
+  {
+#if BLOCKCHAIN_DB == DB_LMDB
+    HardFork::State state = m_blockchain_storage.get_hard_fork_state();
+    switch (state) {
+      case HardFork::LikelyForked:
+        LOG_PRINT_L0(ENDL
+          << "**********************************************************************" << ENDL
+          << "Last scheduled hard fork is too far in the past." << ENDL
+          << "We are most likely forked from the network. Daemon update needed now." << ENDL
+          << "**********************************************************************" << ENDL);
+        break;
+      case HardFork::UpdateNeeded:
+        LOG_PRINT_L0(ENDL
+          << "**********************************************************************" << ENDL
+          << "Last scheduled hard fork time shows a daemon update is needed now." << ENDL
+          << "**********************************************************************" << ENDL);
+        break;
+      default:
+        break;
+    }
+#endif
+    return true;
+  }
+  //-----------------------------------------------------------------------------------------------
   void core::set_target_blockchain_height(uint64_t target_blockchain_height)
   {
     m_target_blockchain_height = target_blockchain_height;
diff --git a/src/cryptonote_core/cryptonote_core.h b/src/cryptonote_core/cryptonote_core.h
index d700b3b4..634340a3 100644
--- a/src/cryptonote_core/cryptonote_core.h
+++ b/src/cryptonote_core/cryptonote_core.h
@@ -69,7 +69,7 @@ namespace cryptonote
      bool prepare_handle_incoming_blocks(const std::list<block_complete_entry>  &blocks);
      bool cleanup_handle_incoming_blocks(bool force_sync = false);
      	     	
-     bool check_incoming_block_size(const blobdata& block_blob);
+     bool check_incoming_block_size(const blobdata& block_blob) const;
      i_cryptonote_protocol* get_protocol(){return m_pprotocol;}
 
      //-------------------- i_miner_handler -----------------------
@@ -78,6 +78,7 @@ namespace cryptonote
 
 
      miner& get_miner(){return m_miner;}
+     const miner& get_miner()const{return m_miner;}
      static void init_options(boost::program_options::options_description& desc);
      bool init(const boost::program_options::variables_map& vm);
      bool set_genesis_block(const block& b);
@@ -86,55 +87,57 @@ namespace cryptonote
      static bool get_fast_exit();
      void test_drop_download();
      void test_drop_download_height(uint64_t height);
-     bool get_test_drop_download();
-     bool get_test_drop_download_height();
-     uint64_t get_current_blockchain_height();
-     bool get_blockchain_top(uint64_t& heeight, crypto::hash& top_id);
-     bool get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks, std::list<transaction>& txs);
-     bool get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks);
+     bool get_test_drop_download() const;
+     bool get_test_drop_download_height() const;
+     uint64_t get_current_blockchain_height() const;
+     bool get_blockchain_top(uint64_t& heeight, crypto::hash& top_id) const;
+     bool get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks, std::list<transaction>& txs) const;
+     bool get_blocks(uint64_t start_offset, size_t count, std::list<block>& blocks) const;
      template<class t_ids_container, class t_blocks_container, class t_missed_container>
-     bool get_blocks(const t_ids_container& block_ids, t_blocks_container& blocks, t_missed_container& missed_bs)
+     bool get_blocks(const t_ids_container& block_ids, t_blocks_container& blocks, t_missed_container& missed_bs) const
      {
        return m_blockchain_storage.get_blocks(block_ids, blocks, missed_bs);
      }
-     crypto::hash get_block_id_by_height(uint64_t height);
-     bool get_transactions(const std::vector<crypto::hash>& txs_ids, std::list<transaction>& txs, std::list<crypto::hash>& missed_txs);
-     bool get_block_by_hash(const crypto::hash &h, block &blk);
+     crypto::hash get_block_id_by_height(uint64_t height) const;
+     bool get_transactions(const std::vector<crypto::hash>& txs_ids, std::list<transaction>& txs, std::list<crypto::hash>& missed_txs) const;
+     bool get_block_by_hash(const crypto::hash &h, block &blk) const;
      //void get_all_known_block_ids(std::list<crypto::hash> &main, std::list<crypto::hash> &alt, std::list<crypto::hash> &invalid);
 
-     bool get_alternative_blocks(std::list<block>& blocks);
-     size_t get_alternative_blocks_count();
+     bool get_alternative_blocks(std::list<block>& blocks) const;
+     size_t get_alternative_blocks_count() const;
 
      void set_cryptonote_protocol(i_cryptonote_protocol* pprotocol);
      void set_checkpoints(checkpoints&& chk_pts);
      void set_checkpoints_file_path(const std::string& path);
      void set_enforce_dns_checkpoints(bool enforce_dns);
 
-     bool get_pool_transactions(std::list<transaction>& txs);
+     bool get_pool_transactions(std::list<transaction>& txs) const;
      bool get_pool_transactions_and_spent_keys_info(std::vector<tx_info>& tx_infos, std::vector<spent_key_image_info>& key_image_infos) const;
-     size_t get_pool_transactions_count();
-     size_t get_blockchain_total_transactions();
+     size_t get_pool_transactions_count() const;
+     size_t get_blockchain_total_transactions() const;
      //bool get_outs(uint64_t amount, std::list<crypto::public_key>& pkeys);
-     bool have_block(const crypto::hash& id);
-     bool get_short_chain_history(std::list<crypto::hash>& ids);
-     bool find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, NOTIFY_RESPONSE_CHAIN_ENTRY::request& resp);
-     bool find_blockchain_supplement(const uint64_t req_start_block, const std::list<crypto::hash>& qblock_ids, std::list<std::pair<block, std::list<transaction> > >& blocks, uint64_t& total_height, uint64_t& start_height, size_t max_count);
-     bool get_stat_info(core_stat_info& st_inf);
+     bool have_block(const crypto::hash& id) const;
+     bool get_short_chain_history(std::list<crypto::hash>& ids) const;
+     bool find_blockchain_supplement(const std::list<crypto::hash>& qblock_ids, NOTIFY_RESPONSE_CHAIN_ENTRY::request& resp) const;
+     bool find_blockchain_supplement(const uint64_t req_start_block, const std::list<crypto::hash>& qblock_ids, std::list<std::pair<block, std::list<transaction> > >& blocks, uint64_t& total_height, uint64_t& start_height, size_t max_count) const;
+     bool get_stat_info(core_stat_info& st_inf) const;
      //bool get_backward_blocks_sizes(uint64_t from_height, std::vector<size_t>& sizes, size_t count);
-     bool get_tx_outputs_gindexs(const crypto::hash& tx_id, std::vector<uint64_t>& indexs);
-     crypto::hash get_tail_id();
-     bool get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::request& req, COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::response& res);
+     bool get_tx_outputs_gindexs(const crypto::hash& tx_id, std::vector<uint64_t>& indexs) const;
+     crypto::hash get_tail_id() const;
+     bool get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::request& req, COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::response& res) const;
      void pause_mine();
      void resume_mine();
 #if BLOCKCHAIN_DB == DB_LMDB
      Blockchain& get_blockchain_storage(){return m_blockchain_storage;}
+     const Blockchain& get_blockchain_storage()const{return m_blockchain_storage;}
 #else
      blockchain_storage& get_blockchain_storage(){return m_blockchain_storage;}
+     const blockchain_storage& get_blockchain_storage()const{return m_blockchain_storage;}
 #endif
      //debug functions
-     void print_blockchain(uint64_t start_index, uint64_t end_index);
-     void print_blockchain_index();
-     std::string print_pool(bool short_format);
+     void print_blockchain(uint64_t start_index, uint64_t end_index) const;
+     void print_blockchain_index() const;
+     std::string print_pool(bool short_format) const;
      void print_blockchain_outs(const std::string& file);
      void on_synchronized();
 
@@ -145,28 +148,29 @@ namespace cryptonote
 
      void stop();
 
-     bool is_key_image_spent(const crypto::key_image& key_im);
-     bool are_key_images_spent(const std::vector<crypto::key_image>& key_im, std::vector<bool> &spent);
+     bool is_key_image_spent(const crypto::key_image& key_im) const;
+     bool are_key_images_spent(const std::vector<crypto::key_image>& key_im, std::vector<bool> &spent) const;
 
    private:
      bool add_new_tx(const transaction& tx, const crypto::hash& tx_hash, const crypto::hash& tx_prefix_hash, size_t blob_size, tx_verification_context& tvc, bool keeped_by_block);
      bool add_new_tx(const transaction& tx, tx_verification_context& tvc, bool keeped_by_block);
      bool add_new_block(const block& b, block_verification_context& bvc);
      bool load_state_data();
-     bool parse_tx_from_blob(transaction& tx, crypto::hash& tx_hash, crypto::hash& tx_prefix_hash, const blobdata& blob);
+     bool parse_tx_from_blob(transaction& tx, crypto::hash& tx_hash, crypto::hash& tx_prefix_hash, const blobdata& blob) const;
 
-     bool check_tx_syntax(const transaction& tx);
+     bool check_tx_syntax(const transaction& tx) const;
      //check correct values, amounts and all lightweight checks not related with database
-     bool check_tx_semantic(const transaction& tx, bool keeped_by_block);
+     bool check_tx_semantic(const transaction& tx, bool keeped_by_block) const;
      //check if tx already in memory pool or in main blockchain
 
-     bool check_tx_ring_signature(const txin_to_key& tx, const crypto::hash& tx_prefix_hash, const std::vector<crypto::signature>& sig);
-     bool is_tx_spendtime_unlocked(uint64_t unlock_time);
+     bool check_tx_ring_signature(const txin_to_key& tx, const crypto::hash& tx_prefix_hash, const std::vector<crypto::signature>& sig) const;
+     bool is_tx_spendtime_unlocked(uint64_t unlock_time) const;
      bool update_miner_block_template();
      bool handle_command_line(const boost::program_options::variables_map& vm);
      bool on_update_blocktemplate_interval();
-     bool check_tx_inputs_keyimages_diff(const transaction& tx);
+     bool check_tx_inputs_keyimages_diff(const transaction& tx) const;
      void graceful_exit();
+     bool check_fork_time();
      static std::atomic<bool> m_fast_exit;
      bool m_test_drop_download = true;
 	 uint64_t m_test_drop_download_height = 0;
@@ -185,6 +189,7 @@ namespace cryptonote
      std::string m_config_folder;
      cryptonote_protocol_stub m_protocol_stub;
      epee::math_helper::once_a_time_seconds<60*60*12, false> m_store_blockchain_interval;
+     epee::math_helper::once_a_time_seconds<60*60*2, false> m_fork_moaner;
      friend class tx_validate_inputs;
      std::atomic<bool> m_starter_message_showed;
 
diff --git a/src/cryptonote_core/hardfork.cpp b/src/cryptonote_core/hardfork.cpp
new file mode 100644
index 00000000..d2e95b58
--- /dev/null
+++ b/src/cryptonote_core/hardfork.cpp
@@ -0,0 +1,267 @@
+// Copyright (c) 2015, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <algorithm>
+#include <cstdio>
+
+#include "cryptonote_core/cryptonote_basic.h"
+#include "blockchain_db/blockchain_db.h"
+#include "hardfork.h"
+
+using namespace cryptonote;
+
+HardFork::HardFork(cryptonote::BlockchainDB &db, uint8_t original_version, time_t forked_time, time_t update_time, uint64_t window_size, int threshold_percent):
+  db(db),
+  original_version(original_version),
+  forked_time(forked_time),
+  update_time(update_time),
+  window_size(window_size),
+  threshold_percent(threshold_percent)
+{
+}
+
+bool HardFork::add(uint8_t version, uint64_t height, time_t time)
+{
+  CRITICAL_REGION_LOCAL(lock);
+
+  // add in order
+  if (version == 0)
+    return false;
+  if (!heights.empty()) {
+    if (version <= heights.back().version)
+      return false;
+    if (height <= heights.back().height)
+      return false;
+    if (time <= heights.back().time)
+      return false;
+  }
+  heights.push_back({version: version, height: height, time: time});
+  return true;
+}
+
+uint8_t HardFork::get_effective_version(const cryptonote::block &block) const
+{
+  uint8_t version = block.major_version;
+  if (!heights.empty()) {
+    uint8_t max_version = heights.back().version;
+    if (version > max_version)
+      version = max_version;
+  }
+  return version;
+}
+
+bool HardFork::do_check(const cryptonote::block &block) const
+{
+  return block.major_version >= heights[current_fork_index].version;
+}
+
+bool HardFork::check(const cryptonote::block &block) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  return do_check(block);
+}
+
+bool HardFork::add(const cryptonote::block &block, uint64_t height)
+{
+  CRITICAL_REGION_LOCAL(lock);
+
+  if (!do_check(block))
+    return false;
+
+  const uint8_t version = get_effective_version(block);
+
+  while (versions.size() >= window_size) {
+    const uint8_t old_version = versions.front();
+    last_versions[old_version]--;
+    assert(last_versions[old_version] >= 0);
+    versions.pop_front();
+  }
+
+  last_versions[version]++;
+  versions.push_back(version);
+
+  uint8_t voted = get_voted_fork_index(height);
+  if (voted > current_fork_index) {
+    for (int v = heights[current_fork_index].version + 1; v <= heights[voted].version; ++v) {
+      db.set_hard_fork_starting_height(v, height);
+    }
+    current_fork_index = voted;
+  }
+
+  db.set_hard_fork_version(height, heights[current_fork_index].version);
+
+  return true;
+}
+
+void HardFork::init()
+{
+  CRITICAL_REGION_LOCAL(lock);
+  versions.clear();
+  for (size_t n = 0; n < 256; ++n)
+    last_versions[n] = 0;
+  current_fork_index = 0;
+  vote_threshold = (uint32_t)ceilf(window_size * threshold_percent / 100.0f);
+
+  // restore state from DB
+  uint64_t height = db.height();
+  if (height > window_size)
+    height -= window_size;
+  else
+    height = 1;
+
+  bool populate = db.get_hard_fork_starting_height(original_version) == std::numeric_limits<uint64_t>::max();
+  if (populate) {
+    LOG_PRINT_L0("The DB has no hard fork info, reparsing from start");
+    height = 1;
+  }
+  LOG_PRINT_L1("reorganizing from " << height);
+  reorganize_from_chain_height(height);
+  if (populate) {
+    // reorg will not touch the genesis block, use this as a flag for populating done
+    db.set_hard_fork_version(0, original_version);
+    db.set_hard_fork_starting_height(original_version, 0);
+  }
+  LOG_PRINT_L1("reorganization done");
+}
+
+bool HardFork::reorganize_from_block_height(uint64_t height)
+{
+  CRITICAL_REGION_LOCAL(lock);
+  if (height >= db.height())
+    return false;
+
+  versions.clear();
+
+  for (size_t n = 0; n < 256; ++n)
+    last_versions[n] = 0;
+  const uint64_t rescan_height = height >= (window_size - 1) ? height - (window_size - 1) : 0;
+  const uint8_t start_version = height == 0 ? original_version : db.get_hard_fork_version(height);
+  while (heights[current_fork_index].version > start_version) {
+    db.set_hard_fork_starting_height(heights[current_fork_index].version, std::numeric_limits<uint64_t>::max());
+    --current_fork_index;
+  }
+  for (uint64_t h = rescan_height; h <= height; ++h) {
+    cryptonote::block b = db.get_block_from_height(h);
+    const uint8_t v = get_effective_version(b);
+    last_versions[v]++;
+    versions.push_back(v);
+  }
+  const uint64_t bc_height = db.height();
+  for (uint64_t h = height + 1; h < bc_height; ++h) {
+    add(db.get_block_from_height(h), h);
+  }
+
+  return true;
+}
+
+bool HardFork::reorganize_from_chain_height(uint64_t height)
+{
+  if (height == 0)
+    return false;
+  return reorganize_from_block_height(height - 1);
+}
+
+int HardFork::get_voted_fork_index(uint64_t height) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  uint32_t accumulated_votes = 0;
+  for (unsigned int n = heights.size() - 1; n > current_fork_index; --n) {
+    uint8_t v = heights[n].version;
+    accumulated_votes += last_versions[v];
+    if (height >= heights[n].height && accumulated_votes >= vote_threshold) {
+      return n;
+    }
+  }
+  return current_fork_index;
+}
+
+HardFork::State HardFork::get_state(time_t t) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+
+  // no hard forks setup yet
+  if (heights.size() <= 1)
+    return Ready;
+
+  time_t t_last_fork = heights.back().time;
+  if (t >= t_last_fork + forked_time)
+    return LikelyForked;
+  if (t >= t_last_fork + update_time)
+    return UpdateNeeded;
+  return Ready;
+}
+
+HardFork::State HardFork::get_state() const
+{
+  return get_state(time(NULL));
+}
+
+uint8_t HardFork::get(uint64_t height) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  if (height > db.height()) {
+    assert(false);
+    return 255;
+  }
+  return db.get_hard_fork_version(height);
+}
+
+uint64_t HardFork::get_start_height(uint8_t version) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  return db.get_hard_fork_starting_height(version);
+}
+
+uint8_t HardFork::get_current_version() const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  return heights[current_fork_index].version;
+}
+
+uint8_t HardFork::get_ideal_version() const
+{
+  CRITICAL_REGION_LOCAL(lock);
+  return heights.back().version;
+}
+
+bool HardFork::get_voting_info(uint8_t version, uint32_t &window, uint32_t &votes, uint32_t &threshold, uint8_t &voting) const
+{
+  CRITICAL_REGION_LOCAL(lock);
+
+  const uint8_t current_version = heights[current_fork_index].version;
+  const bool enabled = current_version >= version;
+  window = versions.size();
+  votes = 0;
+  for (size_t n = version; n < 256; ++n)
+      votes += last_versions[n];
+  threshold = vote_threshold;
+  assert((votes >= threshold) == enabled);
+  voting = heights.back().version;
+  return enabled;
+}
+
diff --git a/src/cryptonote_core/hardfork.h b/src/cryptonote_core/hardfork.h
new file mode 100644
index 00000000..bdac87f2
--- /dev/null
+++ b/src/cryptonote_core/hardfork.h
@@ -0,0 +1,216 @@
+// Copyright (c) 2015, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once
+
+#include "syncobj.h"
+#include "cryptonote_core/cryptonote_basic.h"
+
+namespace cryptonote
+{
+  class BlockchainDB;
+
+  class HardFork
+  {
+  public:
+    typedef enum {
+      LikelyForked,
+      UpdateNeeded,
+      Ready,
+    } State;
+
+    static const time_t DEFAULT_FORKED_TIME = 31557600; // a year in seconds
+    static const time_t DEFAULT_UPDATE_TIME = 31557600 / 2;
+    static const uint64_t DEFAULT_WINDOW_SIZE = 50; // supermajority window check length
+    static const int DEFAULT_THRESHOLD_PERCENT = 80;
+
+    /**
+     * @brief creates a new HardFork object
+     *
+     * @param original_version the block version for blocks 0 through to the first fork
+     * @param forked_time the time in seconds before thinking we're forked
+     * @param update_time the time in seconds before thinking we need to update
+     * @param window_size the size of the window in blocks to consider for version voting
+     * @param threshold_percent the size of the majority in percents
+     */
+    HardFork(cryptonote::BlockchainDB &db, uint8_t original_version = 1, time_t forked_time = DEFAULT_FORKED_TIME, time_t update_time = DEFAULT_UPDATE_TIME, uint64_t window_size = DEFAULT_WINDOW_SIZE, int threshold_percent = DEFAULT_THRESHOLD_PERCENT);
+
+    /**
+     * @brief add a new hardfork height
+     *
+     * returns true if no error, false otherwise
+     *
+     * @param version the major block version for the fork
+     * @param height The height the hardfork takes effect
+     * @param time Approximate time of the hardfork (seconds since epoch)
+     */
+    bool add(uint8_t version, uint64_t height, time_t time);
+
+    /**
+     * @brief initialize the object
+     *
+     * Must be done after adding all the required hardforks via add above
+     */
+    void init();
+
+    /**
+     * @brief check whether a new block would be accepted
+     *
+     * returns true if the block is accepted, false otherwise
+     *
+     * @param block the new block
+     *
+     * This check is made by add. It is exposed publicly to allow
+     * the caller to inexpensively check whether a block would be
+     * accepted or rejected by its version number. Indeed, if this
+     * check could only be done as part of add, the caller would
+     * either have to add the block to the blockchain first, then
+     * call add, then have to pop the block from the blockchain if
+     * its version did not satisfy the hard fork requirements, or
+     * call add first, then, if the hard fork requirements are met,
+     * add the block to the blockchain, upon which a failure (the
+     * block being invalid, double spending, etc) would cause the
+     * hardfork object to reorganize.
+     */
+    bool check(const cryptonote::block &block) const;
+
+    /**
+     * @brief add a new block
+     *
+     * returns true if no error, false otherwise
+     *
+     * @param block the new block
+     */
+    bool add(const cryptonote::block &block, uint64_t height);
+
+    /**
+     * @brief called when the blockchain is reorganized
+     *
+     * This will rescan the blockchain to determine which hard forks
+     * have been triggered
+     *
+     * returns true if no error, false otherwise
+     *
+     * @param blockchain the blockchain
+     * @param height of the last block kept from the previous blockchain
+     */
+    bool reorganize_from_block_height(uint64_t height);
+    bool reorganize_from_chain_height(uint64_t height);
+
+    /**
+     * @brief returns current state at the given time
+     *
+     * Based on the approximate time of the last known hard fork,
+     * estimate whether we need to update, or if we're way behind
+     *
+     * @param t the time to consider
+     */
+    State get_state(time_t t) const;
+    State get_state() const;
+
+    /**
+     * @brief returns the hard fork version for the given block height
+     *
+     * @param height height of the block to check
+     */
+    uint8_t get(uint64_t height) const;
+
+    /**
+     * @brief returns the height of the first block on the fork with th given version
+     *
+     * @param version version of the fork to query the starting block for
+     */
+    uint64_t get_start_height(uint8_t version) const;
+
+    /**
+     * @brief returns the latest "ideal" version
+     *
+     * This is the latest version that's been scheduled
+     */
+    uint8_t get_ideal_version() const;
+
+    /**
+     * @brief returns the current version
+     *
+     * This is the latest version that's past its trigger date and had enough votes
+     * at one point in the past.
+     */
+    uint8_t get_current_version() const;
+
+    /**
+     * @brief returns information about current voting state
+     *
+     * returns true if the given version is enabled (ie, the current version
+     * is at least the passed version), false otherwise
+     *
+     * @param version the version to check voting for
+     * @param window the number of blocks considered in voting
+     * @param votes number of votes for next version
+     * @param threshold number of votes needed to switch to next version
+     */
+    bool get_voting_info(uint8_t version, uint32_t &window, uint32_t &votes, uint32_t &threshold, uint8_t &voting) const;
+
+    /**
+     * @brief returns the size of the voting window in blocks
+     */
+    uint64_t get_window_size() const { return window_size; }
+
+  private:
+
+    bool do_check(const cryptonote::block &block) const;
+    int get_voted_fork_index(uint64_t height) const;
+    uint8_t get_effective_version(const cryptonote::block &block) const;
+
+  private:
+
+    BlockchainDB &db;
+
+    time_t forked_time;
+    time_t update_time;
+    uint64_t window_size;
+    int threshold_percent;
+
+    uint8_t original_version;
+
+    typedef struct {
+      uint8_t version;
+      uint64_t height;
+      time_t time;
+    } Params;
+    std::vector<Params> heights;
+
+    std::deque<uint8_t> versions; /* rolling window of the last N blocks' versions */
+    unsigned int last_versions[256]; /* count of the block versions in the last N blocks */
+    uint32_t current_fork_index;
+    uint32_t vote_threshold;
+
+    mutable epee::critical_section lock;
+  };
+
+}  // namespace cryptonote
+
diff --git a/src/daemon/command_parser_executor.cpp b/src/daemon/command_parser_executor.cpp
index e6666c44..7b0f4a66 100644
--- a/src/daemon/command_parser_executor.cpp
+++ b/src/daemon/command_parser_executor.cpp
@@ -361,5 +361,27 @@ bool t_command_parser_executor::stop_save_graph(const std::vector<std::string>&
 	return m_executor.stop_save_graph();
 }
 
+bool t_command_parser_executor::hard_fork_info(const std::vector<std::string>& args)
+{
+  int version;
+  if (args.size() == 0) {
+    version = 0;
+  }
+  else if (args.size() == 1) {
+    try {
+      version = std::stoi(args[0]);
+    }
+    catch(std::invalid_argument& ex) {
+        return false;
+    }
+    if (version <= 0 || version > 255)
+      return false;
+  }
+  else {
+    return false;
+  }
+  return m_executor.hard_fork_info(version);
+}
+
 
 } // namespace daemonize
diff --git a/src/daemon/command_parser_executor.h b/src/daemon/command_parser_executor.h
index ddc207cf..f900c72b 100644
--- a/src/daemon/command_parser_executor.h
+++ b/src/daemon/command_parser_executor.h
@@ -102,6 +102,8 @@ public:
   bool start_save_graph(const std::vector<std::string>& args);
   
   bool stop_save_graph(const std::vector<std::string>& args);
+  
+  bool hard_fork_info(const std::vector<std::string>& args);
 };
 
 } // namespace daemonize
diff --git a/src/daemon/command_server.cpp b/src/daemon/command_server.cpp
index 047b52c3..44637955 100644
--- a/src/daemon/command_server.cpp
+++ b/src/daemon/command_server.cpp
@@ -184,6 +184,11 @@ t_command_server::t_command_server(
     , std::bind(&t_command_parser_executor::stop_save_graph, &m_parser, p::_1)
     , "Stop save data for dr monero"
     );
+    m_command_lookup.set_handler(
+      "hard_fork_info"
+    , std::bind(&t_command_parser_executor::hard_fork_info, &m_parser, p::_1)
+    , "Print hard fork voting information"
+    );
 }
 
 bool t_command_server::process_command_str(const std::string& cmd)
diff --git a/src/daemon/rpc_command_executor.cpp b/src/daemon/rpc_command_executor.cpp
index 62f254c7..c4fe642e 100644
--- a/src/daemon/rpc_command_executor.cpp
+++ b/src/daemon/rpc_command_executor.cpp
@@ -946,4 +946,35 @@ bool t_rpc_command_executor::stop_save_graph()
 	return true;
 }
 
+bool t_rpc_command_executor::hard_fork_info(uint8_t version)
+{
+    cryptonote::COMMAND_RPC_HARD_FORK_INFO::request req;
+    cryptonote::COMMAND_RPC_HARD_FORK_INFO::response res;
+    std::string fail_message = "Unsuccessful";
+    epee::json_rpc::error error_resp;
+
+    req.version = version;
+
+    if (m_is_rpc)
+    {
+        if (!m_rpc_client->json_rpc_request(req, res, "/hard_fork_info", fail_message.c_str()))
+        {
+            return true;
+        }
+    }
+    else
+    {
+        if (!m_rpc_server->on_hard_fork_info(req, res, error_resp))
+        {
+            tools::fail_msg_writer() << fail_message.c_str();
+            return true;
+        }
+        version = version > 0 ? version : res.voting;
+        tools::msg_writer() << "version " << (uint32_t)version << " " << (res.enabled ? "enabled" : "not enabled") <<
+            ", " << res.votes << "/" << res.window << " votes, threshold " << res.threshold;
+        tools::msg_writer() << "current version " << (uint32_t)res.version << ", voting for version " << (uint32_t)res.voting;
+    }
+    return true;
+}
+
 }// namespace daemonize
diff --git a/src/daemon/rpc_command_executor.h b/src/daemon/rpc_command_executor.h
index b40a67bf..9ad84943 100644
--- a/src/daemon/rpc_command_executor.h
+++ b/src/daemon/rpc_command_executor.h
@@ -120,6 +120,8 @@ public:
   bool start_save_graph();
   
   bool stop_save_graph();
+  
+  bool hard_fork_info(uint8_t version);
 };
 
 } // namespace daemonize
diff --git a/src/rpc/core_rpc_server.cpp b/src/rpc/core_rpc_server.cpp
index 80bd7e6c..f9ff632a 100644
--- a/src/rpc/core_rpc_server.cpp
+++ b/src/rpc/core_rpc_server.cpp
@@ -812,6 +812,29 @@ namespace cryptonote
     return true;
   }
   //------------------------------------------------------------------------------------------------------------------------------
+  bool core_rpc_server::on_hard_fork_info(const COMMAND_RPC_HARD_FORK_INFO::request& req, COMMAND_RPC_HARD_FORK_INFO::response& res, epee::json_rpc::error& error_resp)
+  {
+    if(!check_core_busy())
+    {
+      error_resp.code = CORE_RPC_ERROR_CODE_CORE_BUSY;
+      error_resp.message = "Core is busy.";
+      return false;
+    }
+
+#if BLOCKCHAIN_DB == DB_LMDB
+    const Blockchain &blockchain = m_core.get_blockchain_storage();
+    uint8_t version = req.version > 0 ? req.version : blockchain.get_ideal_hard_fork_version();
+    res.version = blockchain.get_current_hard_fork_version();
+    res.enabled = blockchain.get_hard_fork_voting_info(version, res.window, res.votes, res.threshold, res.voting);
+    res.state = blockchain.get_hard_fork_state();
+    return true;
+#else
+    error_resp.code = CORE_RPC_ERROR_CODE_UNSUPPORTED_RPC;
+    error_resp.message = "Hard fork inoperative in memory mode.";
+    return false;
+#endif
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
   bool core_rpc_server::on_fast_exit(const COMMAND_RPC_FAST_EXIT::request& req, COMMAND_RPC_FAST_EXIT::response& res)
   {
 	  cryptonote::core::set_fast_exit();
diff --git a/src/rpc/core_rpc_server.h b/src/rpc/core_rpc_server.h
index 3213e6b1..60e7d00d 100644
--- a/src/rpc/core_rpc_server.h
+++ b/src/rpc/core_rpc_server.h
@@ -138,6 +138,7 @@ namespace cryptonote
     bool on_get_block_header_by_height(const COMMAND_RPC_GET_BLOCK_HEADER_BY_HEIGHT::request& req, COMMAND_RPC_GET_BLOCK_HEADER_BY_HEIGHT::response& res, epee::json_rpc::error& error_resp);
     bool on_get_connections(const COMMAND_RPC_GET_CONNECTIONS::request& req, COMMAND_RPC_GET_CONNECTIONS::response& res, epee::json_rpc::error& error_resp);
     bool on_get_info_json(const COMMAND_RPC_GET_INFO::request& req, COMMAND_RPC_GET_INFO::response& res, epee::json_rpc::error& error_resp);
+    bool on_hard_fork_info(const COMMAND_RPC_HARD_FORK_INFO::request& req, COMMAND_RPC_HARD_FORK_INFO::response& res, epee::json_rpc::error& error_resp);
     //-----------------------
 
 private:
diff --git a/src/rpc/core_rpc_server_commands_defs.h b/src/rpc/core_rpc_server_commands_defs.h
index b2fdd993..a806cbae 100644
--- a/src/rpc/core_rpc_server_commands_defs.h
+++ b/src/rpc/core_rpc_server_commands_defs.h
@@ -815,5 +815,40 @@ namespace cryptonote
       END_KV_SERIALIZE_MAP()
     };
   };
+
+  struct COMMAND_RPC_HARD_FORK_INFO
+  {
+    struct request
+    {
+      uint8_t version;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(version)
+      END_KV_SERIALIZE_MAP()
+    };
+
+    struct response
+    {
+      uint8_t version;
+      bool enabled;
+      uint32_t window;
+      uint32_t votes;
+      uint32_t threshold;
+      uint8_t voting;
+      uint32_t state;
+      std::string status;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(version)
+        KV_SERIALIZE(enabled)
+        KV_SERIALIZE(window)
+        KV_SERIALIZE(votes)
+        KV_SERIALIZE(threshold)
+        KV_SERIALIZE(voting)
+        KV_SERIALIZE(state)
+        KV_SERIALIZE(status)
+      END_KV_SERIALIZE_MAP()
+    };
+  };
 }
 
diff --git a/src/rpc/core_rpc_server_error_codes.h b/src/rpc/core_rpc_server_error_codes.h
index 91659eb2..72c72b94 100644
--- a/src/rpc/core_rpc_server_error_codes.h
+++ b/src/rpc/core_rpc_server_error_codes.h
@@ -40,5 +40,6 @@
 #define CORE_RPC_ERROR_CODE_BLOCK_NOT_ACCEPTED    -7
 #define CORE_RPC_ERROR_CODE_CORE_BUSY             -9
 #define CORE_RPC_ERROR_CODE_WRONG_BLOCKBLOB_SIZE  -10
+#define CORE_RPC_ERROR_CODE_UNSUPPORTED_RPC       -11
 
 
diff --git a/tests/unit_tests/CMakeLists.txt b/tests/unit_tests/CMakeLists.txt
index 2c6f1865..bbfa4a90 100644
--- a/tests/unit_tests/CMakeLists.txt
+++ b/tests/unit_tests/CMakeLists.txt
@@ -46,7 +46,8 @@ set(unit_tests_sources
   slow_memmem.cpp
   test_format_utils.cpp
   test_peerlist.cpp
-  test_protocol_pack.cpp)
+  test_protocol_pack.cpp
+  hardfork.cpp)
 
 set(unit_tests_headers
   unit_tests_utils.h)
diff --git a/tests/unit_tests/hardfork.cpp b/tests/unit_tests/hardfork.cpp
new file mode 100644
index 00000000..ad00ed60
--- /dev/null
+++ b/tests/unit_tests/hardfork.cpp
@@ -0,0 +1,452 @@
+// Copyright (c) 2014-2015, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+// 
+// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
+
+#include <algorithm>
+#include "gtest/gtest.h"
+
+#include "blockchain_db/lmdb/db_lmdb.h"
+#include "cryptonote_core/hardfork.h"
+
+using namespace cryptonote;
+
+#define BLOCKS_PER_YEAR 525960
+#define SECONDS_PER_YEAR 31557600
+
+
+class TestDB: public BlockchainDB {
+public:
+  virtual void open(const std::string& filename, const int db_flags = 0) {
+    for (size_t n = 0; n < 256; ++n)
+      starting_height[n] = std::numeric_limits<uint64_t>::max();
+  }
+  virtual void close() {}
+  virtual void sync() {}
+  virtual void reset() {}
+  virtual std::vector<std::string> get_filenames() const { return std::vector<std::string>(); }
+  virtual std::string get_db_name() const { return std::string(); }
+  virtual bool lock() { return true; }
+  virtual void unlock() { }
+  virtual void batch_start(uint64_t batch_num_blocks=0) {}
+  virtual void batch_stop() {}
+  virtual void set_batch_transactions(bool) {}
+  virtual bool block_exists(const crypto::hash& h) const { return false; }
+  virtual block get_block(const crypto::hash& h) const { return block(); }
+  virtual uint64_t get_block_height(const crypto::hash& h) const { return 0; }
+  virtual block_header get_block_header(const crypto::hash& h) const { return block_header(); }
+  virtual uint64_t get_block_timestamp(const uint64_t& height) const { return 0; }
+  virtual uint64_t get_top_block_timestamp() const { return 0; }
+  virtual size_t get_block_size(const uint64_t& height) const { return 128; }
+  virtual difficulty_type get_block_cumulative_difficulty(const uint64_t& height) const { return 10; }
+  virtual difficulty_type get_block_difficulty(const uint64_t& height) const { return 0; }
+  virtual uint64_t get_block_already_generated_coins(const uint64_t& height) const { return 10000000000; }
+  virtual crypto::hash get_block_hash_from_height(const uint64_t& height) const { return crypto::hash(); }
+  virtual std::vector<block> get_blocks_range(const uint64_t& h1, const uint64_t& h2) const { return std::vector<block>(); }
+  virtual std::vector<crypto::hash> get_hashes_range(const uint64_t& h1, const uint64_t& h2) const { return std::vector<crypto::hash>(); }
+  virtual crypto::hash top_block_hash() const { return crypto::hash(); }
+  virtual block get_top_block() const { return block(); }
+  virtual uint64_t height() const { return blocks.size(); }
+  virtual bool tx_exists(const crypto::hash& h) const { return false; }
+  virtual uint64_t get_tx_unlock_time(const crypto::hash& h) const { return 0; }
+  virtual transaction get_tx(const crypto::hash& h) const { return transaction(); }
+  virtual uint64_t get_tx_count() const { return 0; }
+  virtual std::vector<transaction> get_tx_list(const std::vector<crypto::hash>& hlist) const { return std::vector<transaction>(); }
+  virtual uint64_t get_tx_block_height(const crypto::hash& h) const { return 0; }
+  virtual uint64_t get_num_outputs(const uint64_t& amount) const { return 1; }
+  virtual output_data_t get_output_key(const uint64_t& amount, const uint64_t& index) { return output_data_t(); }
+  virtual output_data_t get_output_key(const uint64_t& global_index) const { return output_data_t(); }
+  virtual tx_out get_output(const crypto::hash& h, const uint64_t& index) const { return tx_out(); }
+  virtual tx_out_index get_output_tx_and_index_from_global(const uint64_t& index) const { return tx_out_index(); }
+  virtual tx_out_index get_output_tx_and_index(const uint64_t& amount, const uint64_t& index) { return tx_out_index(); }
+  virtual void get_output_tx_and_index(const uint64_t& amount, const std::vector<uint64_t> &offsets, std::vector<tx_out_index> &indices) {}
+  virtual void get_output_key(const uint64_t &amount, const std::vector<uint64_t> &offsets, std::vector<output_data_t> &outputs) {}
+  virtual bool can_thread_bulk_indices() const { return false; }
+  virtual std::vector<uint64_t> get_tx_output_indices(const crypto::hash& h) const { return std::vector<uint64_t>(); }
+  virtual std::vector<uint64_t> get_tx_amount_output_indices(const crypto::hash& h) const { return std::vector<uint64_t>(); }
+  virtual bool has_key_image(const crypto::key_image& img) const { return false; }
+  virtual void remove_block() { blocks.pop_back(); }
+  virtual void add_transaction_data(const crypto::hash& blk_hash, const transaction& tx, const crypto::hash& tx_hash) {}
+  virtual void remove_transaction_data(const crypto::hash& tx_hash, const transaction& tx) {}
+  virtual void add_output(const crypto::hash& tx_hash, const tx_out& tx_output, const uint64_t& local_index, const uint64_t unlock_time) {}
+  virtual void remove_output(const tx_out& tx_output) {}
+  virtual void add_spent_key(const crypto::key_image& k_image) {}
+  virtual void remove_spent_key(const crypto::key_image& k_image) {}
+
+  virtual void add_block( const block& blk
+                        , const size_t& block_size
+                        , const difficulty_type& cumulative_difficulty
+                        , const uint64_t& coins_generated
+                        , const crypto::hash& blk_hash
+                        ) {
+    blocks.push_back(blk);
+  }
+  virtual block get_block_from_height(const uint64_t& height) const {
+    return blocks[height];
+  }
+  virtual void set_hard_fork_starting_height(uint8_t version, uint64_t height) {
+    starting_height[version] = height;
+  }
+  virtual uint64_t get_hard_fork_starting_height(uint8_t version) const {
+    return starting_height[version];
+  }
+  virtual void set_hard_fork_version(uint64_t height, uint8_t version) {
+    printf("set_hard_fork_version(%lu, %u)\n", (unsigned long)height, version);
+    if (versions.size() <= height) versions.resize(height+1); versions[height] = version;
+  }
+  virtual uint8_t get_hard_fork_version(uint64_t height) const {
+    printf("get_hard_fork_version(%lu)\n", (unsigned long)height);
+    return versions[height];
+  }
+
+private:
+  std::vector<block> blocks;
+  uint64_t starting_height[256];
+  std::deque<uint8_t> versions;
+};
+
+static cryptonote::block mkblock(uint8_t version)
+{
+  cryptonote::block b;
+  b.major_version = version;
+  return b;
+}
+
+TEST(empty_hardforks, Success)
+{
+  TestDB db;
+  HardFork hf(db);
+
+  ASSERT_TRUE(hf.add(1, 0, 0));
+  hf.init();
+  ASSERT_TRUE(hf.get_state(time(NULL)) == HardFork::Ready);
+  ASSERT_TRUE(hf.get_state(time(NULL) + 3600*24*400) == HardFork::Ready);
+
+  for (uint64_t h = 0; h <= 10; ++h) {
+    db.add_block(mkblock(1), 0, 0, 0, crypto::hash());
+    ASSERT_TRUE(hf.add(db.get_block_from_height(h), h));
+  }
+  ASSERT_EQ(hf.get(0), 1);
+  ASSERT_EQ(hf.get(1), 1);
+  ASSERT_EQ(hf.get(10), 1);
+}
+
+TEST(ordering, Success)
+{
+  TestDB db;
+  HardFork hf(db);
+
+  ASSERT_TRUE(hf.add(2, 2, 1));
+  ASSERT_FALSE(hf.add(3, 3, 1));
+  ASSERT_FALSE(hf.add(3, 2, 2));
+  ASSERT_FALSE(hf.add(2, 3, 2));
+  ASSERT_TRUE(hf.add(3, 10, 2));
+  ASSERT_TRUE(hf.add(4, 20, 3));
+  ASSERT_FALSE(hf.add(5, 5, 4));
+}
+
+TEST(states, Success)
+{
+  TestDB db;
+  HardFork hf(db);
+
+  ASSERT_TRUE(hf.add(1, 0, 0));
+  ASSERT_TRUE(hf.add(2, BLOCKS_PER_YEAR, SECONDS_PER_YEAR));
+
+  ASSERT_TRUE(hf.get_state(0) == HardFork::Ready);
+  ASSERT_TRUE(hf.get_state(SECONDS_PER_YEAR / 2) == HardFork::Ready);
+  ASSERT_TRUE(hf.get_state(SECONDS_PER_YEAR + HardFork::DEFAULT_UPDATE_TIME / 2) == HardFork::Ready);
+  ASSERT_TRUE(hf.get_state(SECONDS_PER_YEAR + (HardFork::DEFAULT_UPDATE_TIME + HardFork::DEFAULT_FORKED_TIME) / 2) == HardFork::UpdateNeeded);
+  ASSERT_TRUE(hf.get_state(SECONDS_PER_YEAR + HardFork::DEFAULT_FORKED_TIME * 2) == HardFork::LikelyForked);
+
+  ASSERT_TRUE(hf.add(3, BLOCKS_PER_YEAR * 5, SECONDS_PER_YEAR * 5));
+
+  ASSERT_TRUE(hf.get_state(0) == HardFork::Ready);
+  ASSERT_TRUE(hf.get_state(SECONDS_PER_YEAR / 2) == HardFork::Ready);
+  ASSERT_TRUE(hf.get_state(SECONDS_PER_YEAR + HardFork::DEFAULT_UPDATE_TIME / 2) == HardFork::Ready);
+  ASSERT_TRUE(hf.get_state(SECONDS_PER_YEAR + (HardFork::DEFAULT_UPDATE_TIME + HardFork::DEFAULT_FORKED_TIME) / 2) == HardFork::Ready);
+  ASSERT_TRUE(hf.get_state(SECONDS_PER_YEAR + HardFork::DEFAULT_FORKED_TIME * 2) == HardFork::Ready);
+}
+
+TEST(steps_asap, Success)
+{
+  TestDB db;
+  HardFork hf(db, 1,1,1,1);
+
+  //                 v  h  t
+  ASSERT_TRUE(hf.add(1, 0, 0));
+  ASSERT_TRUE(hf.add(4, 2, 1));
+  ASSERT_TRUE(hf.add(7, 4, 2));
+  ASSERT_TRUE(hf.add(9, 6, 3));
+  hf.init();
+
+  for (uint64_t h = 0; h < 10; ++h) {
+    db.add_block(mkblock(10), 0, 0, 0, crypto::hash());
+    ASSERT_TRUE(hf.add(db.get_block_from_height(h), h));
+  }
+
+  ASSERT_EQ(hf.get(0), 1);
+  ASSERT_EQ(hf.get(1), 1);
+  ASSERT_EQ(hf.get(2), 4);
+  ASSERT_EQ(hf.get(3), 4);
+  ASSERT_EQ(hf.get(4), 7);
+  ASSERT_EQ(hf.get(5), 7);
+  ASSERT_EQ(hf.get(6), 9);
+  ASSERT_EQ(hf.get(7), 9);
+  ASSERT_EQ(hf.get(8), 9);
+  ASSERT_EQ(hf.get(9), 9);
+}
+
+TEST(steps_1, Success)
+{
+  TestDB db;
+  HardFork hf(db, 1,1,1,1);
+
+  ASSERT_TRUE(hf.add(1, 0, 0));
+  for (int n = 1 ; n < 10; ++n)
+    ASSERT_TRUE(hf.add(n+1, n, n));
+  hf.init();
+
+  for (uint64_t h = 0 ; h < 10; ++h) {
+    db.add_block(mkblock(h+1), 0, 0, 0, crypto::hash());
+    ASSERT_TRUE(hf.add(db.get_block_from_height(h), h));
+  }
+
+  for (uint64_t h = 0; h < 10; ++h) {
+    ASSERT_EQ(hf.get(h), h+1);
+  }
+}
+
+TEST(reorganize, Same)
+{
+  for (int history = 1; history <= 12; ++history) {
+    TestDB db;
+    HardFork hf(db, 1, 1, 1, history, 100);
+
+    //                 v  h  t
+    ASSERT_TRUE(hf.add(1, 0, 0));
+    ASSERT_TRUE(hf.add(4, 2, 1));
+    ASSERT_TRUE(hf.add(7, 4, 2));
+    ASSERT_TRUE(hf.add(9, 6, 3));
+    hf.init();
+
+    //                                 index  0  1  2  3  4  5  6  7  8  9
+    static const uint8_t block_versions[] = { 1, 1, 4, 4, 7, 7, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9 };
+    for (uint64_t h = 0; h < 20; ++h) {
+      db.add_block(mkblock(block_versions[h]), 0, 0, 0, crypto::hash());
+      ASSERT_TRUE(hf.add(db.get_block_from_height(h), h));
+    }
+
+    for (uint64_t rh = 0; rh < 20; ++rh) {
+      hf.reorganize_from_block_height(rh);
+      for (int hh = 0; hh < 20; ++hh) {
+        uint8_t version = hh >= (history-1) ? block_versions[hh - (history-1)] : 1;
+        ASSERT_EQ(hf.get(hh), version);
+      }
+    }
+  }
+}
+
+TEST(reorganize, Changed)
+{
+  int history = 4;
+  TestDB db;
+  HardFork hf(db, 1, 1, 1, 4, 100);
+
+  //                 v  h  t
+  ASSERT_TRUE(hf.add(1, 0, 0));
+  ASSERT_TRUE(hf.add(4, 2, 1));
+  ASSERT_TRUE(hf.add(7, 4, 2));
+  ASSERT_TRUE(hf.add(9, 6, 3));
+  hf.init();
+
+  //                                 index  0  1  2  3  4  5  6  7  8  9
+  static const uint8_t block_versions[] = { 1, 1, 4, 4, 7, 7, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9 };
+  for (uint64_t h = 0; h < 16; ++h) {
+    db.add_block(mkblock(block_versions[h]), 0, 0, 0, crypto::hash());
+    ASSERT_TRUE (hf.add(db.get_block_from_height(h), h));
+  }
+
+  for (uint64_t rh = 0; rh < 16; ++rh) {
+    hf.reorganize_from_block_height(rh);
+    for (int hh = 0; hh < 16; ++hh) {
+      uint8_t version = hh >= (history-1) ? block_versions[hh - (history-1)] : 1;
+      ASSERT_EQ(hf.get(hh), version);
+    }
+  }
+
+  // delay a bit for 9, and go back to 1 to check it stays at 9
+  static const uint8_t block_versions_new[] =    { 1, 1, 4, 4, 7, 7, 4, 7, 7, 7, 9, 9, 9, 9, 9, 1 };
+  static const uint8_t expected_versions_new[] = { 1, 1, 1, 1, 1, 4, 4, 4, 4, 4, 7, 7, 7, 9, 9, 9 };
+  for (uint64_t h = 3; h < 16; ++h) {
+    db.remove_block();
+  }
+  ASSERT_EQ(db.height(), 3);
+  hf.reorganize_from_block_height(2);
+  for (uint64_t h = 3; h < 16; ++h) {
+    db.add_block(mkblock(block_versions_new[h]), 0, 0, 0, crypto::hash());
+    bool ret = hf.add(db.get_block_from_height(h), h);
+    ASSERT_EQ (ret, h < 15);
+  }
+  db.remove_block(); // last block added to the blockchain, but not hf
+  ASSERT_EQ(db.height(), 15);
+  for (int hh = 0; hh < 15; ++hh) {
+    ASSERT_EQ(hf.get(hh), expected_versions_new[hh]);
+  }
+}
+
+TEST(voting, threshold)
+{
+  for (int threshold = 87; threshold <= 88; ++threshold) {
+    TestDB db;
+    HardFork hf(db, 1, 1, 1, 8, threshold);
+
+    //                 v  h  t
+    ASSERT_TRUE(hf.add(1, 0, 0));
+    ASSERT_TRUE(hf.add(2, 2, 1));
+    hf.init();
+
+    for (uint64_t h = 0; h <= 8; ++h) {
+      uint8_t v = 1 + !!(h % 8);
+      db.add_block(mkblock(v), 0, 0, 0, crypto::hash());
+      bool ret = hf.add(db.get_block_from_height(h), h);
+      if (h >= 8 && threshold == 87) {
+        ASSERT_FALSE(ret);
+      }
+      else {
+        ASSERT_TRUE(ret);
+        uint8_t expected = threshold == 88 ? 1 : h < 7 ? 1 : 2;
+        ASSERT_EQ(hf.get(h), expected);
+      }
+    }
+  }
+}
+
+TEST(new_blocks, denied)
+{
+    TestDB db;
+    HardFork hf(db, 1, 1, 1, 4, 50);
+
+    //                 v  h  t
+    ASSERT_TRUE(hf.add(1, 0, 0));
+    ASSERT_TRUE(hf.add(2, 2, 1));
+    hf.init();
+
+    ASSERT_FALSE(hf.add(mkblock(0), 0));
+    ASSERT_TRUE(hf.add(mkblock(1), 0));
+    ASSERT_TRUE(hf.add(mkblock(1), 1));
+    ASSERT_TRUE(hf.add(mkblock(1), 2));
+    ASSERT_TRUE(hf.add(mkblock(2), 3));
+    ASSERT_TRUE(hf.add(mkblock(1), 4));
+    ASSERT_TRUE(hf.add(mkblock(1), 5));
+    ASSERT_TRUE(hf.add(mkblock(1), 6));
+    ASSERT_TRUE(hf.add(mkblock(2), 7));
+    ASSERT_TRUE(hf.add(mkblock(2), 8)); // we reach 50% of the last 4
+    ASSERT_FALSE(hf.add(mkblock(1), 9)); // so this one can't get added
+    ASSERT_TRUE(hf.add(mkblock(2), 10));
+
+    ASSERT_EQ(hf.get_start_height(2), 8);
+}
+
+TEST(new_version, early)
+{
+    TestDB db;
+    HardFork hf(db, 1, 1, 1, 4, 50);
+
+    //                 v  h  t
+    ASSERT_TRUE(hf.add(1, 0, 0));
+    ASSERT_TRUE(hf.add(2, 4, 1));
+    hf.init();
+
+    ASSERT_FALSE(hf.add(mkblock(0), 0));
+    ASSERT_TRUE(hf.add(mkblock(2), 0));
+    ASSERT_TRUE(hf.add(mkblock(2), 1)); // we have enough votes already
+    ASSERT_TRUE(hf.add(mkblock(2), 2));
+    ASSERT_TRUE(hf.add(mkblock(1), 3)); // we accept a previous version because we did not switch, even with all the votes
+    ASSERT_TRUE(hf.add(mkblock(2), 4)); // but have to wait for the declared height anyway
+    ASSERT_TRUE(hf.add(mkblock(2), 5));
+    ASSERT_FALSE(hf.add(mkblock(1), 6)); // we don't accept 1 anymore
+    ASSERT_TRUE(hf.add(mkblock(2), 7)); // but we do accept 2
+
+    ASSERT_EQ(hf.get_start_height(2), 4);
+}
+
+TEST(reorganize, changed)
+{
+    TestDB db;
+    HardFork hf(db, 1, 1, 1, 4, 50);
+
+    //                 v  h  t
+    ASSERT_TRUE(hf.add(1, 0, 0));
+    ASSERT_TRUE(hf.add(2, 2, 1));
+    ASSERT_TRUE(hf.add(3, 5, 2));
+    hf.init();
+
+#define ADD(v, h, a) \
+  do { \
+    cryptonote::block b = mkblock(v); \
+    db.add_block(b, 0, 0, 0, crypto::hash()); \
+    ASSERT_##a(hf.add(b, h)); \
+  } while(0)
+#define ADD_TRUE(v, h) ADD(v, h, TRUE)
+#define ADD_FALSE(v, h) ADD(v, h, FALSE)
+
+    ADD_FALSE(0, 0);
+    ADD_TRUE(1, 0);
+    ADD_TRUE(1, 1);
+    ADD_TRUE(2, 2);
+    ADD_TRUE(2, 3); // switch to 2 here
+    ADD_TRUE(2, 4);
+    ADD_TRUE(2, 5);
+    ADD_TRUE(2, 6);
+    ASSERT_EQ(hf.get_current_version(), 2);
+    ADD_TRUE(3, 7);
+    ADD_TRUE(4, 8);
+    ADD_TRUE(4, 9);
+    ASSERT_EQ(hf.get_start_height(2), 3);
+    ASSERT_EQ(hf.get_start_height(3), 8);
+    ASSERT_EQ(hf.get_current_version(), 3);
+
+    // pop a few blocks and check current version goes back down
+    db.remove_block();
+    hf.reorganize_from_block_height(8);
+    ASSERT_EQ(hf.get_current_version(), 3);
+    db.remove_block();
+    hf.reorganize_from_block_height(7);
+    ASSERT_EQ(hf.get_current_version(), 2);
+    db.remove_block();
+    ASSERT_EQ(hf.get_current_version(), 2);
+
+    // add blocks again, but remaining at 2
+    ADD_TRUE(2, 7);
+    ADD_TRUE(2, 8);
+    ADD_TRUE(2, 9);
+    ASSERT_EQ(hf.get_start_height(2), 3); // unchanged
+    ASSERT_EQ(hf.get_current_version(), 2); // we did not bump to 3 this time
+    ASSERT_EQ(hf.get_start_height(3), std::numeric_limits<uint64_t>::max()); // not yet
+}