Why does the date for Easter change every year?

And what exactly does it have to do with the moon?
Why does the date for Easter change every year?
Image credit: Carol Redford

in 2018, Easter Sunday coincides with April Fool’s Day!

But there’s no need to be fooled about why the Easter date changes every year.

Easter Date Calculation

Easter Sunday is the first Sunday after the full Moon, following the March equinox (which is always on or around 22nd March every year).

There’s a bit of calculation involved, so here’s how it works for 2018:

  • The March equinox is on the 21st of March at precisely 12:15am (WA time).
  • The full Moon after this date is on Saturday, 31st March
  • Easter Sunday is always the Sunday after the full moon, which is April 1st, 2018!

What is an Equinox?

An equinox is when the centre of our Sun is on exactly the same plane as Earth’s equator. The Earth’s axis isn’t tilted toward the Sun one way or the other and the hours of night and day are almost equal in length. Another thing to note at equinox is that sunrise is due east and sunset is due west.

This article was originally published by Galaxy Girl, Carol Redford, on the Stargazers Club WA website.


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