Try this one: https://www.timeanddate.com/holidays/common/easter-sunday
Easter wasn’t a holiday until Constantine declared in 326 c.e. the day is celebrated differently between Eastern Orthodox and Catholic depending on the Gregorian or Julian Calendar. It was declared a holiday because the Last Supper was a Passover Seder and He was presented as a Passover Lamb Sacrifice. Since that time, however, many other doctrines crept into the Symbology, which is Resurrection, new life, a new beginning, etc. To this day, however, Easter has little to do with Passover. Passover is always the same day, always on the 15th of Nissan, always a full moon. They needed the full moon to escape Egypt through the desert and it took the length of Passover(8 days) to get to the reed sea.
The Council of Nicaea set the rules for determining the date of Easter...which is why Pope Gregory's calendar reform in 1582 was designed to return the date of the vernal equinox to where it had been in A.D. 325 rather than to where it was in 46 B.C. when Julius Caesar reformed the Roman calendar.
That the Anglo-Saxons, when they became Christians, took over the name of a pagan spring festival and applied it to a Christian feast is unimportant. Likewise, the English word "Lent" originally just meant "spring"--other languages have a term for Lent based on the number 40 for the length of Lent.
Dutch lente means "spring." The Dutch word for Lent is vasten, from the word meaning "to fast."
The connection between Lent and spring is that it is the time when the days are growing longer--etymologically it is connected to "long" and "lengthen." Doesn't work in the southern hemisphere.