Easter Date Hunt

[deckardcanine]

Most holidays in Christendom don’t change their date each year,
But Easter’s an exception. Let me make the reason clear.
It’s understood that Jesus’ final meal before he died
Transpired during Passover, whose start is always tied
To Day 15 of Nisan, which requires a full moon
Just past the vernal equinox, except it’s not as soon
In certain years: The lunar cycle needs intercalation,
So sometimes it’s the next full moon (try not to feel frustration).
The ancient system wasn’t so; the feast might come ere spring.
To early Christians, this was quite an inconsistent thing.
Besides, they didn’t want to keep relying on the Jews
To tell them when to worship, so they turned to other cues.
They chose to say the equinox was March the 21st
Each year (I’m hardly certain that they didn’t make things worse).
Resulting drift preceded the Gregorian reform
That made the western calendar that’s nowadays the norm,
But since the Eastern Orthodox kept Julian instead,
The Catholics and Protestants will celebrate ahead
Of those ones by at least a week and often four or five.
My sources give us formulas that help us to derive
The Easter days for many years, but these are too complex
For poetry. I’d rather just look up which date is next.