Gregory the 13th.

It was first reformed by the Italian physicians, astronomers, philosophers, chronologists Aloysius Rilius and Claudius and other scholars on the basis of the Confucian calendar, and subsequently promulgated by Pope Gregory XIII in 1582. and the "Calendar Age" is also known as the "Western". Because the content of the Gregorian calendar is simpler, easy to remember, and is more accurate, and better matched with the times, it is gradually adopted by the governments.

On March 1, 1582, Gregory issued a decree of conversion, which said:

A day after October 4, 1582, was October 15, instead of October 5, but the number of weeks continued to be counted: October 4 was Thursday, the next day October 15 was Friday.

Second, in order to avoid the phenomenon of later spring separation, change the year method to: where the number of years can be fixed by 4 is the year, but when the year behind the number of years is with two "0" "century years", the year must be fixed by 400 is the year.

The average year length of the Gregorian calendar is 365 days, 5 hours 49 minutes 12 seconds, 26 seconds longer than the regression.