import datetime

def genday(dt):
 now = datetime.date.today().strftime("%Y%m%dT000000Z")
 then = dt.strftime("%Y%m%d")
 di = "%i"
 ds = "%s"

 return '''BEGIN:VEVENT
UID:%s@kumig.it
DTSTAMP:%s
DTSTART;VALUE=DATE:%s
SUMMARY:%s days since %s
END:VEVENT
''' % (ds, now, then, di, ds)

def gencal(dt, offset = None, string = None, futuredays = 14):
 offset = offset or (datetime.date.today() - dt).days

 rv = '''BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Klaus-Uwe Mitterer//DaysSince//EN
METHOD:PUBLISH
'''

 for day in range(offset + futuredays):
  rv += genday(dt + datetime.timedelta(days = day)) % ("%i%i%i%i" % (dt.year, dt.month, dt.day, day), day, "%i/%i/%i" % (dt.year, dt.month, dt.day))

 rv += "END:VCALENDAR"

 return rv

def cal(dt, string = None):
 offset = (datetime.date.today() - dt).days

 if offset < 0:
  return ""

 else:
  return iter([gencal(dt, string).replace("\n", "\r\n").encode()])