80歳が寿命だとして。

get_days.py

# coding:utf-8

import datetime


def print_days(birth_year, birth_month, birth_day, target_year):
    birth_day = datetime.date(birth_year, birth_month, birth_day)
    today = datetime.date.today()
    last_day = datetime.date(birth_day.year + target_year, birth_day.month, birth_day.day)
    print last_day
    print "Today", today - birth_day
    print "Last day", last_day - today

if __name__ == '__main__':
    print_days(birth_year=2013, birth_month=7, birth_day=22, target_year=80)