How old am I?

Calculating the age of a person in a web service is harder than one might think to get right. Things you must be aware of are:

Time zones: The time zone at the client is likely not the same as on your machine. Hence it could be that the person is under-age in their country, but already an adult in the server time zone.

Calendar years: Usually we think of one year as 365 days. Hence calculating the age of a person sounds as simple as calculating the days since their birth, dividing by 365 and that's it. Execept that we don't think of age like this.

I challenge you to create a program that solves the following task. I'm interested in your solutions, so please share a link to a gist, pastebin or wherever you solved the task.

Task

Write a program that takes the following input as a ; separated string:

1. Birthday as YYYY-MM-DDTHH:mm:ss, assuming the time zone given
2. Timezone of Birth (IANA name, e.g. Europe/Berlin)
3. Current time as YYYY-MM-DDTHH:mm:ssZ (UTC)

and prints the age in years (a single integer).

Tests

assert get_age("1996-02-29T15:45:54;Europe/Berlin;2018-10-03T09:47:50") == 22
assert get_age("2008-04-28T15:45:54;Europe/Berlin;2018-10-03T09:47:50") == 10
assert get_age("2008-11-28T15:45:54;Europe/Berlin;2018-10-03T09:47:50") == 9
assert get_age("2006-03-01T00:00:00;Europe/Berlin;2008-02-29T23:59:59") == 1

Solutions

I hope to see many solutions in different programming languages.

Python Solution

Author: Martin Thoma

def get_age(input_):
    """
    Calculate the age of a person
    """
    from dateutil.parser import parse
    import pytz

    # parse input
    born, born_tz, now = input_.split(";")
    tz = pytz.timezone(born_tz)
    born = parse(born).replace(tzinfo=pytz.utc).astimezone(tz)
    now = parse(now).replace(tzinfo=pytz.utc)

    # age logic
    year_not_finished = (now.month, now.day) < (born.month, born.day)
    age = now.year - born.year - int(year_not_finished)
    return age