annunciation.py

""" The angel of the Lord declared unto Mary
    and she conceived of the Holy Spirit.
    Behold, the handmaid of the Lord
    Be it done unto me according to Thy word.
    And the Word was made flesh
    and dwelt among us."""

from datetime import *


def get_annunciation_date(year):
    """
    >>> get_annunciation_date(2013)
    datetime.date(2013, 4, 8)    
    """
    christmas = date(year, month=12, day=25)
    annunciation = date(year, month=christmas.month-9, day=christmas.day)
    while is_holy_week(annunciation) or is_easter_octave(annunciation):
        annunciation += timedelta(days=1)
    # the definitions of is_holy_week and is_easter_octave are left
    # as an exercise to the reader.
    # There might be other rules. Here be bugs and dragons...
    return annunciation


def is_holy_week(given_date):
    easter = date(2013, 3, 31)
    return (easter - timedelta(days=7)) <= given_date <= easter


def is_easter_octave(given_date):
    easter = date(2013, 3, 31)
    return easter <= given_date <= (easter + timedelta(days=7))


if __name__ == '__main__':
    print(get_annunciation_date(2013))