I have thought myself knowledgeable regarding Easter and the calendar. I knew that Easter falls on the first Sunday after the first full moon after the vernal equinox. But now I know that knowing that is not knowing enough.
It’s not just any full moon; it’s the Paschal Full Moon based on the Ecclesiastical Moon calendar, a lunisolar calendar which is based on the movements of both the sun and the moon which means Easter must always fall after March 21. Also, Easter may not precede or coincide with the first day of Passover if you're Eastern Orthodox.
So this year, Easter is as early as it can ever be....near ‘bout anyway. It’s on the 23rd and the earliest it can ever be is the 22nd. It won’t be this early again for 152 years. Last time it was any earlier was 1818 and it won’t be any earlier that this date again until 2285
The latest it will ever be is April 25 and the last time it did that was 1943 and will do so again in 2038.
Easter is a movable Christian feast, meaning it floats around the calendar based on calculations of lunar cycles and the solar seasons. Based on our Gregorian calendar, the cycle of Easter repeats itself every 5.7 million years. Easter falls most commonly on April 19 and then less than 4% of the time.
And that is just in the Western Christian Church. Eastern Orthodox Christians have a different calendar (i.e. Passover note above).
When First Council of Nicaea met in 325, the whole point in their setting in motion these intricate calculations was to ensure a standard date for the observance of Easter for all Christian churches in all locations.
There was an easier way. If Peter had turned to Mary as they stood at the door of the empty tomb and just said, “Mary, you know, I will never forget this day...” and then said the date, well, we’d have it.
But there is something about the mystery of the date of Easter that works well with the mystery of the resurrection and of spring and the Earth’s awakening in the blooms and births that abound.
It all adds to the wonderment and keeps us guessing if only a small bit.