Festivals have long included games of chance, from dice at Saturnalia to teen...

https://emilysexpertchat.yousher.com/why-do-calendars-keep-certain-days-open-for-risk-taking

Festivals have long included games of chance, from dice at Saturnalia to teen patti during Diwali and mahjong at Lunar New Year. Setting a clear end date using calendars helped keep gambling part of the celebration, not a year-round problem