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))

To make it clear, this code is licensed as a public domain. Feel free to use it as you wish.

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.