Home > Calendar, Ephemeris Program, Events > 04/15/2022 – Ephemeris – How the date of Easter is determined

04/15/2022 – Ephemeris – How the date of Easter is determined

April 15, 2022

This is Ephemeris for Good Friday, April 15th. Today the Sun will be up for 13 hours and 29 minutes, setting at 8:27, and it will rise tomorrow at 6:56. The Moon, 1 day before full, will set at 7:04 tomorrow morning.

Easter will be celebrated by Western 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 starts at sunset tonight. The western churches adopted the Gregorian calendar to keep in sync with the seasons. The Orthodox churches didn’t, so their Easter is a week later 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). They may be different for your location.

Addendum

If you’re wondering about what all this has to do with astronomy? The answer is: Everything! Astronomy in ancient times wasn’t about the nature of planets, and stars, but about the cycles about the Sun and Moon. These cycles announced the seasons, and festival times. This is how the date of Passover is set. The Jews, at least in the Bible, only referenced the constellations of Orion and the Great Bear plus the star cluster Pleiades, that scholars have pinned down. There are two more possible references to constellations that don’t translate. These are all in the Book of Job. The only planet mentioned is Saturn, because it was thought to be closest to the firmament, the starry sphere.

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