"Aw man, Tray, look up at the sky. It's a full moon. On the Sabbath." -Werewolf Bar Mitzvah

full_moon_sabbath.py

from datetime import date, timedelta

# http://www.voidware.com/moon_phase.htm
def moon_phase(y, m, d):
    """
    0 => new moon
    1 => waxing crescent
    2 => first quarter
    3 => waxing gibbous
    4 => full moon
    5 => waning gibbous
    6 => third quarter
    7 => waning crescent
    """
    if m < 3:
        y -= 1
        m += 12
    m += 1
    c = 365.25 * y
    e = 30.6 * m
    jd = c + e + d - 694039.09
    jd /= 29.53
    b = int(jd)
    jd -= b
    b = jd * 8 + 0.5
    b = int(b) & 7
    return b

today = date(2024, 1, 1)
friday = today + timedelta((4 - today.weekday()) % 7)

for i in range(52*4):
    phase = moon_phase(friday.year, friday.month, friday.day)
    if phase == 4:
        print(friday)
    friday += timedelta(weeks=1)