Czech public holiday checker

isholiday.py

#!/usr/bin/env python3
import datetime

def getholidays(year):
    """Return a set public holidays in CZ as (day, month) tuples."""
    
    holidays = {
                (1, 1),   #Novy rok
                (1, 5),   #Svatek prace
                (8, 5),   #Den vitezstvi
                (5, 7),   #Cyril a Metodej
                (6, 7),   #Jan Hus
                (28, 9),  #Den Ceske statnosti
                (28, 10), #Vznik CS statu
                (17, 11), #Den boje za svobodu a dem.
                (24, 12), #Stedry den
                (25, 12), #1. svatek Vanocni
                (26, 12), #2. svatek Vanocni
               }

    # Easter holiday LUT source http://www.whyeaster.com/customs/dateofeaster.shtml
    easterlut = [(4, 14), (4, 3), (3, 23), (4, 11), (3, 31), (4, 18), (4, 8),
                 (3, 28), (4, 16), (4, 5), (3, 25), (4, 13), (4, 2), (3, 22),
                 (4, 10), (3, 30), (4, 17), (4, 7), (3, 27)]
    easterday = datetime.date(year, *easterlut[year%19])
    daystosunday = 6 - easterday.weekday()
    easterday += datetime.timedelta(7 if daystosunday == 0 else daystosunday)
    # print("Easter Sunday is on ", easterday)
    holidays.update(((d.day, d.month) for d in [easterday - datetime.timedelta(2),
                                                easterday + datetime.timedelta(1)]))
    return holidays

def isholiday(date):
    return (date.day, date.month) in getholidays(date.year)

if __name__ == "__main__":
    for y in range(2016, 2030):
        print("{}: {}".format(y, getholidays(y)))
    testdates = [(2016, 3, 28), (2017, 3, 28), (2017, 4, 14)]
    for date in testdates:
        d = datetime.date(*date)
        print(d.ctime(), isholiday(d))

isholidaynl.py

#!/usr/bin/env python3
import datetime

def getholidays(year, goodfriday=True, liberation="everyfive"):
    """Return a set public holidays in NL as (day, month) tuples."""
    
    holidays = {
                (1, 1),   # New year
                (27, 4),  # Koningsdag
                (25, 12), # Kerst
                (26, 12), # Kerst
               }
    if liberation == True or (liberation == "everyfive" and year % 5 == 0):
        holidays.update([(5,5),])

    # Easter holiday LUT source http://www.whyeaster.com/customs/dateofeaster.shtml
    easterlut = [(4, 14), (4, 3), (3, 23), (4, 11), (3, 31), (4, 18), (4, 8),
                 (3, 28), (4, 16), (4, 5), (3, 25), (4, 13), (4, 2), (3, 22),
                 (4, 10), (3, 30), (4, 17), (4, 7), (3, 27)]
    easterday = datetime.date(year, *easterlut[year % 19])
    daystosunday = 6 - easterday.weekday()
    easterday += datetime.timedelta(7 if daystosunday == 0 else daystosunday)
    # print("Easter Sunday is on ", easterday)
    if goodfriday:
        holidays.update(((d.day, d.month) for d in [
            easterday - datetime.timedelta(2),
        ]))
    holidays.update(((d.day, d.month) for d in [
        easterday, # Easter Sunday
        easterday + datetime.timedelta(1), # Easter Monday
        easterday + datetime.timedelta(39), # Ascension Day
        easterday + datetime.timedelta(49), # Pentecost 1
        easterday + datetime.timedelta(50), # Pentecost 2
    ]))
    return holidays

def isholiday(date):
    return (date.day, date.month) in getholidays(date.year)

if __name__ == "__main__":
    for y in range(2020, 2031):
        print("{}: {}".format(y, sorted(getholidays(y), key=lambda x: x[::-1],)))
    testdates = [(2016, 3, 28), (2017, 3, 28), (2017, 4, 14)]
    for date in testdates:
        d = datetime.date(*date)
        print(d.ctime(), isholiday(d))

It turned out the calculation is broken for 2025. If the LUT lookup results in Sunday, Easter happens one week later not on that Sunday. I updated the code to fix this and also added a version for holidays in NL.