def diff_month(d1, d2):
    return (d1.year - d2.year) * 12 + d1.month - d2.month
assert diff_month(datetime(2010, 10, 1), datetime(2010, 9, 1)) == 1
assert diff_month(datetime(2010, 10, 1), datetime(2009, 10, 1)) == 12
assert diff_month(datetime(2010, 10, 1), datetime(2009, 11, 1)) == 11
assert diff_month(datetime(2010, 10, 1), datetime(2009, 8, 1)) == 14
Best way to find the months between two dates