hldays adds religious and cultural observances to its holiday API

The hldays developer explains that public holidays are legal closures, while religious observances such as Ramadan, Passover and Lunar New Year shape schedules without closing offices. The project added 46 observances across six traditions, served through a dedicated endpoint and attached to date endpoints on paid plans. Each tradition is defined in a YAML file using rule types shared with the holiday engine, including fixed dates, offsets from Easter and dates in other calendars. The post focuses on the calendar calculations, notably the Gregorian and Orthodox Easter algorithms, including the Julian-to-Gregorian shift that remains 13 days across the supported 2016 to 2099 range. Tests check cases such as years when both Easters coincide.