actually, there were...
https://en.wikipedia.org/wiki/Julian_calendar
before the julian calendar it was a complete mess around the world. the expansion of the roman empire until the 8th century and the adoption of catholic beliefe as state religion within the roman empire brought us the calendar we have today
What calendar do the church use that they know when is Easter etc each year?
The clerical calender is based on the easter event. Easter sunday is defined as the first sunday after the first full moon after the spring equinox (now back on track at march 21st).
All other events are placed certain amount of days before/after easter, except for those with a fixed date (e.g. christmas is always december 25th)
It is interesting that the church uses dates based on the sun's analemma and the buddism use a moon calendar. yet we use something different.
Great food for thought article!! thanks!
Indeed an interesting aspect and maybe some time a point of further investigation 😉
Thank you 😊