Zeller's congruence

zeller_congruence.py

"""
https://en.wikipedia.org/wiki/Zeller%27s_congruence
https://zh.wikipedia.org/wiki/%E8%94%A1%E5%8B%92%E5%85%AC%E5%BC%8F
"""
from functools import wraps
from icecream import ic

# h is the day of the week (0 = Saturday, 1 = Sunday, 2 = Monday, ..., 6 = Friday)
WEEK = {0: 'Sun.',
        1: 'Mon.',
        2: 'Tue.',
        3: 'Wed.',
        4: 'Thu.',
        5: 'Fri.',
        6: 'Sat.'}


def fix_month(func):
    """
    m is the month (3 = March, 4 = April, 5 = May, ..., 14 = February)
    """
    @wraps(func)
    def wrapper(*args, **kwargs):
        m = kwargs.get('m')
        if m == 1:
            kwargs.update({'m': 13})
        elif m == 2:
            kwargs.update({'m': 14})
        return func(*args, **kwargs)

    return wrapper


@fix_month
def zeller(c, y, m, d):
    w = (y + y // 4 + c // 4 - 2 * c + (26 * (m + 1) // 10) + d - 1)
    # deal with negative number
    w = (w % 7 + 7) % 7
    return WEEK[w]


if __name__ == '__main__':
    year = 2006
    month = 4
    day = 4
    res = zeller(20, 6, 4, 4)
    ic(res)

# ----
# ic| res: 'Tue.'