Page "Equinox" Paragraph 15

In more detail, the gradual shift to March 11 induced Pope Gregory XIII to create a modern Gregorian calendar.

The Pope was moved by the desire to restore the edicts concerning the date of Easter of the Council of Nicaea of AD 325.

( Incidentally, the date of Easter itself is fixed by an approximation of lunar cycles used in the Hebraic calendar, but according to the historian Bede the English name " Easter " comes from a pagan celebration by the Germanic tribes of the vernal ( spring ) equinox.

) So, the shift in the date of the equinox that occurred between the 4th and the 16th centuries was annulled with the Gregorian calendar, but nothing was done for the first four centuries of the Julian calendar.

The days of February 29 of the years AD 100, AD 200, AD 300, and the day created by the irregular application of leap years between the assassination of Caesar and the decree of Augustus re-arranging the calendar in AD 8, remained in effect.

This moved the equinox four days earlier than in Caesar's time.