An age calculating library

age.py

import datetime
import calendar

def simple_age(birthdate, today=None):
    if today is None:
        today = datetime.date.today()
    #what's this year's birthdate?
    try:
        bd = datetime.date(today.year, birthdate.month, birthdate.day)
    except ValueError:
        #special case 2/29
        bd = datetime.date(today.year, 3, 1)
    if bd <= today:
        return today.year - birthdate.year
    else:
        return today.year - birthdate.year - 1

def get_age(birthdate,today=None):
    start_year = birthdate.year
    if today is None:
        today = datetime.date.today()
    current_year = today.year
    # without modification, calling leapdays will return number of leap days
    # between jan1 start_year and jan 1 current_year
    if calendar.isleap(start_year) and birthdate >= datetime.date(start_year, 2, 29):
        start_year += 1
    if calendar.isleap(current_year) and today >= datetime.date(current_year, 2, 29):
        # if we are past the leap day, we should count the current year's leap day also
        current_year += 1
    leapdays = calendar.leapdays(start_year, current_year)
    return ((today - birthdate).days - leapdays)/ 365

#get_age = simple_age

assert(8 == get_age(datetime.date(1992, 2, 29), datetime.date(2000, 2, 29)))
assert(8 == get_age(datetime.date(1992, 2, 28), datetime.date(2000, 2, 28)))
assert(8 == get_age(datetime.date(1992, 3, 1), datetime.date(2000, 3, 1)))
assert(8 == get_age(datetime.date(1992, 2, 29), datetime.date(2000, 3, 1)))
assert(8 == get_age(datetime.date(1992, 2, 28), datetime.date(2000, 3, 1)))

assert(7 == get_age(datetime.date(1992, 3, 1), datetime.date(2000, 2, 28)))
assert(7 == get_age(datetime.date(1992, 3, 1), datetime.date(2000, 2, 29)))

assert(9 == get_age(datetime.date(1992, 2, 28), datetime.date(2001, 2, 28)))
assert(9 == get_age(datetime.date(1992, 3, 1), datetime.date(2001, 3, 1)))
assert(9 == get_age(datetime.date(1992, 2, 29), datetime.date(2001, 3, 1)))
assert(9 == get_age(datetime.date(1992, 2, 28), datetime.date(2001, 3, 1)))

assert(8 == get_age(datetime.date(1992, 3, 1), datetime.date(2001, 2, 28)))