XKCD 2018

calculate_xkcd_2018.py

import sys
from datetime import date,timedelta


def is_xkcd_day(d):
    return d.weekday() in {0, 2, 4}


def find_date_by_xkcd_number(xkcd_num, current_xkcd=1964, start_date=date(2018, 3, 7)):
    if not is_xkcd_day(start_date):
        raise Exception("start_date must be an xkcd day (M, W, F")
    xkcds_until_target = xkcd_num - current_xkcd
    d = start_date
    xkcd_counter = 0
    date_with_xkcd_num = None

    while True:
        if xkcd_counter == xkcds_until_target:
            if not is_xkcd_day(d):
                d = d + timedelta(days=1)
                continue
            date_with_xkcd_num = d
            break

        d = d + timedelta(days=1)
        if is_xkcd_day(d):
            xkcd_counter += 1

    return date_with_xkcd_num

if __name__ == '__main__':
    xkcd_to_find = int(sys.argv[1]) if len(sys.argv) > 1 else 2018
    xkcd_date = find_date_by_xkcd_number(xkcd_to_find)
    print('Date of XKCD #{}: {}'.format(xkcd_to_find, xkcd_date))

usage.md

The date of XKCD number 2018 will be July 11, 2018

[caleb@cmbpr:Tests]$ python3 xkcd_2018.py
Date of XKCD #2018: 2018-07-11

Other tests

[caleb@cmbpr:Tests]$ python3 xkcd_2018.py 1964
Date of XKCD #1964: 2018-03-07
[caleb@cmbpr:Tests]$ python3 xkcd_2018.py 1965
Date of XKCD #1965: 2018-03-09
[caleb@cmbpr:Tests]$ python3 xkcd_2018.py 1966
Date of XKCD #1966: 2018-03-12