>>> import calendar
>>> calendar.monthrange(2002,1)
(1, 31)
>>> calendar.monthrange(2008,2)
(4, 29)
>>> calendar.monthrange(2100,2)
(0, 28)
 
>>> calendar.monthrange(2016, 2)[1]

import datetime
for x in xrange(1, 13):
  dt_start = (datetime.datetime(2016, x, 1)).strftime("%Y%m%d")
  if 12 == x:
    dt_end = (datetime.datetime(2016, 12, 31)).strftime("%Y%m%d")
  else:
    dt_end = (datetime.datetime(2016, x+1, 1) - datetime.timedelta(days = 1)).strftime("%Y%m%d")
  print dt_start, dt_end