diff --git a/crontab/_crontab.py b/crontab/_crontab.py
index 0eb2d26..528809e 100644
--- a/crontab/_crontab.py
+++ b/crontab/_crontab.py
@@ -435,16 +435,16 @@ class CronTab(object):
             "crontab: %r\n" \
             "now: %r", ' '.join(m.input for m in self.matchers), now)
 
+        if not delta:
+            onow = now = datetime(1970, 1, 1)
+
         delay = future - now
         if tz:
-            delay += onow.utcoffset()
-            delay -= tz.localize(future).utcoffset()
-
-        if not delta:
-            begin = datetime(1970, 1, 1)
-            delay = future - begin
-            if tz:
-                delay -= tz.localize(future).utcoffset()
+            delay += _fix_none(onow.utcoffset())
+            if hasattr(tz, 'localize'):
+                delay -= _fix_none(tz.localize(future).utcoffset())
+            else:
+                delay -= _fix_none(future.replace(tzinfo=tz).utcoffset())
 
         return delay.days * 86400 + delay.seconds + delay.microseconds / 1000000.
 
@@ -458,3 +458,8 @@ class CronTab(object):
             if not self._test_match(index, entry):
                 return False
         return True
+
+def _fix_none(d, _=timedelta(0)):
+    if d is None:
+        return _
+    return d
diff --git a/setup.py b/setup.py
index 7347685..5545920 100644
--- a/setup.py
+++ b/setup.py
@@ -10,7 +10,7 @@ except:
 
 setup(
     name='crontab',
-    version='0.22.3',
+    version='0.22.4',
     description='Parse and use crontab schedules in Python',
     author='Josiah Carlson',
     author_email='josiah.carlson@gmail.com',
diff --git a/tests/test_crontab.py b/tests/test_crontab.py
index 4117173..8c0e97d 100644
--- a/tests/test_crontab.py
+++ b/tests/test_crontab.py
@@ -4,6 +4,7 @@ import datetime
 import unittest
 
 import pytz
+import dateutil.tz
 
 from crontab import CronTab
 
@@ -171,7 +172,7 @@ class TestCrontab(unittest.TestCase):
             self.assertTrue(-3600 <= previous <= 0, previous)
             ts += datetime.timedelta(seconds=1)
 
-    def test_timezones(self):
+    def test_timezones_pytz(self):
         s = CronTab('0 9 13 3 * 2016')
 
         self.assertEqual(s.next(datetime.datetime(2016, 3, 13), default_utc=True), 32400)
@@ -189,6 +190,27 @@ class TestCrontab(unittest.TestCase):
         self.assertEqual(CronTab('30 1 * * * 2018').next(timezone.localize(datetime.datetime(2018, 11, 4, 1, 15))), 900)
         self.assertEqual(CronTab('30 1 * * * 2018').next(timezone.localize(datetime.datetime(2018, 11, 4))), 9000)
 
+    def test_timezones_dateutil(self):
+        s = CronTab('0 9 13 3 * 2016')
+
+        self.assertEqual(s.next(datetime.datetime(2016, 3, 13), default_utc=True), 32400)
+        utc = dateutil.tz.tzutc()
+        self.assertEqual(s.next(datetime.datetime(2016, 3, 13, tzinfo=utc), default_utc=True), 32400)
+
+        x = datetime.datetime(2016, 3, 13, tzinfo=dateutil.tz.gettz('US/Eastern'))
+        self.assertEqual(s.next(x), 28800)
+
+        t = CronTab('0 9 * * * 2018')
+        self.assertEqual(t.next(datetime.datetime(2018, 11, 4), default_utc=True), 32400)
+
+        timezone = dateutil.tz.gettz("America/Los_Angeles")
+        self.assertEqual(t.next(datetime.datetime(2018, 11, 4, tzinfo=timezone)), 36000)
+        before = datetime.datetime(2018, 11, 4, 8, 29, tzinfo=utc).astimezone(timezone)
+        self.assertEqual(CronTab('30 1 * * * 2018').next(before), 60)
+        before = datetime.datetime(2018, 11, 4, 8, 31, tzinfo=utc).astimezone(timezone)
+        self.assertEqual(CronTab('30 1 * * * 2018').next(before), 89940)
+        self.assertEqual(CronTab('30 1 * * * 2018').next(datetime.datetime(2018, 11, 4, 1, 15, tzinfo=timezone)), 900)
+        self.assertEqual(CronTab('30 1 * * * 2018').next(datetime.datetime(2018, 11, 4, tzinfo=timezone)), 5400)
 
 if __name__ == '__main__':
     unittest.main()