It should be somewhat easy to figure out.
If you go by the Jewish Calendar, Easter always falls on the first Sunday after Passover.
I believe that was how they calculated it back in 329 AD. It was the first Sunday following Nisan 14 (
https://www.hope-of-israel.org/nisan14p.htm).
Another way of putting it, according to the Bible, Jesus Christ's death and resurrection occurred at the time of the Jewish Passover, which was celebrated on the first Full Moon following the Vernal Equinox.
I don't have (yet) an algorithm to figure this one out, but someone clever could figure this out.
Good Luck.
So if you know when Nisan 14 was in 329 AD, then you know when Easter was first celebrated after the Council of
Cobalt.
That could be tricky for a couple of reasons. The world, as a whole, had adapted the Gregorian Calendar as of 1582. Before then we had a length of year of about 375 days. "Oh. But what about using Julian days?", you may ask. If memory serves correctly, Julian days are measured from the start of an epoch (usually data recorded at a specific point in time. Usually at the beginning of a Century).
Determining events based on Pre-Gregorian (Julian) could be inaccurate... after all, from the second to the 16th century, most scholars were using a geocentric system (everything rotated around the Earth).
But that being said, calculating the day of the 'first' Easter may not be possible. Easter was a pagan festival that pre-dated the Christian religion. There are many symbols adopted by many cultures. Easter has roots in a Spring festival to the godess Eostre and the Jewish holiday of Passover. Records show that Christians adopted and observed, the current form of Easter, as early as the second century AD. But parts of it may have had its roots as far back as the first century AD.
My apologies for 'babbling'... I really must concentrate on brevity...
J
