>>> from dates import age, complete_year, age_21

>>> e = age_21(10, 4, 1990, 23, 5, 13)
>>> e
23
>>> e = age_21(10, 4, 3, 5, 3, 2013)
>>> e
9
>>> e = age_21(10, 4, 1998, 23, 5, 13)
>>> e
15
>>> e = age_21(10, 4, 3, 5, 3, 2016)
>>> e
12