Home > Calendar, Celebration, Ephemeris Program > Ephemeris: 04/18/2025 – How the date of Easter is calculated

Ephemeris: 04/18/2025 – How the date of Easter is calculated

April 18, 2025

This is Ephemeris for Good Friday, Friday, April 18th. Today the Sun will be up for 13 hours and 39 minutes, setting at 8:32, and it will rise tomorrow at 6:51. The Moon, 2 days before last quarter, will rise at 2:40 tomorrow morning.

Easter will be celebrated by all Christian churches this Sunday. Easter is a movable feast in that it falls on a different date each year following the first full moon of spring. It’s an attempt to follow the Jewish Passover, which starts on the 15th of the month of Nisan. The Jewish calendar being a lunar calendar, the 15th is generally the night of the full moon. And since the Last Supper was a Seder, according to at least one Gospel, the Christian church wanted to link Easter with Passover as closely as possible using the Roman solar based (Julian) calendar. The months didn’t follow the cycle of the Moon anymore and where the year was 365.25 days long. Passover started at sunset last Sunday. The western churches adopted the Gregorian calendar to keep in sync with the seasons. The Orthodox churches didn’t, but Easter is so late that they match this year. They kept the old Julian Calendar and other considerations to calculate the date of Easter.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.

Addendum

The Germanic goddess of spring and dawn Oestre
This is the Germanic goddess of spring and dawn Oestre, from whose name we get the word Easter. Since the dawn arrives from the east, I think the word East may come from her name too. As far as I’ve been able to check the name of the feast of the Resurrection is related to the Passover in most other European countries. Credit: Ostara (Oestre) by Johannes Gehrts (1855–1921), via Wikipedia.

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