Festivals have long been a time for gambling, but cultures often used calendars...

https://www.bookmark-xray.win/festivals-have-long-been-a-time-for-games-of-chance-from-saturnalia-s-dice-to

Festivals have long been a time for gambling, but cultures often used calendars to mark clear endings for bets and games. For example, during Saturnalia in ancient Rome, gambling was allowed only until the festival’s close