Check Age

from datetime import datetime

class Datestuff:  # dummy class

    isleap = lambda year: year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)

    @staticmethod
    def age_check(birth_date:str, cutoff_year:int=18) -> int:
        """return whole age of person given string date yyyy-mm-dd"""
        try:
            year, month, day = [int(numstr) for numstr in birth_date.split("-")]
        except ValueError:
            raise ValueError(f'{birth_date} in not in required yyyy-mm-dd format')  # pass up the chain

        # further validations
        if not 1910 <= year <= datetime.now().date().year:
            raise ValueError(f'Someone born in {year} is not alive today')
        if not 1 <= month <= 12:
            raise ValueError(f'{month} is not a valid month number')
        if not 1 <= day <= 31:
            raise ValueError(f'{day} is not a valid day number')
        if month == 2 and day == 29 and not isleap(year):
            raise ValueError(f'invalid date - {year} is not a leap year')
        if (day > 29 if month == 2 else 31) and month not in [1, 3, 5,7,8,10,12]:
            raise ValueError(f'invalid date - not {day} days in month {month}')

        today = datetime.now().date()

        age = 0
        if today.year > year:
            age = today.year - year
            if today.month < month or (today.month == month and today.day < day):
                age -= 1

        return age

    @classmethod
    def is_18(cls, birth_date:str) -> bool:
        """return if age determined from birthdate yyyy-mm-dd is >= 18 """
        return cls.age_check(birth_date) >= 18

eg = Datestuff()
tests = ["1999/12/10", "1863-12-10", "1995-13-05", "1995-12-00",
         "2019-02-29", "2019-02-30", "2016-07-29",
         "2000-01-01", "2000-04-31"
        ]
print('\n\nCheck for valid birthdates and return age:\n')
for test in tests:
    try:
        print(f'Born: {test}, age: {eg.age_check(test)}')
    except ValueError as e:
        print(f'Born: {test} - ERROR: {e}')

print('\n\nCheck for valid birthdates and confirm if age >= 18:\n')
for test in tests:
    try:
        print(f'Born: {test}, old enough: {"yes" if eg.is_18(test) else "no"}')
    except ValueError as e:
        print(f'Born: {test} - ERROR: {e}')