How did the Catholics find the leap years?

Hello;

When Gregory XIII commissioned a calendar that added leap days to keep holy days in line with the seasons, how did mathematicians choose which years needed a 366th day? I found a base 12 calendar of 60 6-day weeks with leap days scattered through the year, and its inventors said that you can't just tack on six more days every few years because it'd throw the calendar off the seasons, but not how they knew that.

 

They know this because the time it takes for the earth to travel around the sun "in a year", is a fraction not a whole number. The reason for the leap years is to keep a given calendar year from containing a fractional day. Hard to have a half of a day. They then edited to fit the "holy" days.

 

Right, I get that, but could you have 360-day calendar years with 6-day leap weeks every few years?

 

Yep! you could in fact set it up any way you wished. Certain setups however would require you to alter the length of days as well as weeks. Yet would also in certain systems have to do away with the 12 hour clock, and use another system. It would be nice if some one hear could tell you what would be required to create the system you want.

Alonzo perhaps?