Easter Formula

[daydreamer]

What is the purpose for that? Background for a computer game?

Right now I working on asm program that creates greyscale heightmaps for import in 3d landscape program

Sounds a bit like George Lucas.

the start of art interest was to make sprites,tiles,backgrounds and evolved to a nice relaxing hobby,but recent game art is lowpoly 3d models
its my interest of someday make a tiny demo that use lot of procedural creation and right now inspired by Carl Sagan tv series about space had Cg animations

I also coded the easter algo before,it seems like long ago it was the real full moon,but it now seem like a hypothetical fullmoon?,but today enough for calculate when easter shall be in calendar ?and that will suffice for churches

its nice to have document for lay persons,but programmers interest in formulas,could be instead in comments?

[Gunther]

daydreamer,

I also coded the easter algo before,it seems like long ago it was the real full moon,but it now seem like a hypothetical fullmoon?

Yes. Easter isn't determined according to the exact, astronomical course of the moon, but according to a simplified course. It can therefore happen that Easter is celebrated astronomically at the wrong time.
The ecclesiastical Easter reckoning uses for its calculations the fact that 19 revolutions of the earth around the sun (casually: 19 years) correspond quite exactly to 235 synodic months:

• 19 ∙ 365.24219 = 6939.6016 days or 6939 days and 14.439 hours
• 235 ∙ 29.53059 days = 6939.6887 days or 6939 days and 16.528 hours

Only after about 11.5 cycles or about 218 years, this small difference of about 2 hours will have added up to 1 day. This cycle of 19 years is called after its discoverer, the Astronomer Meton of Athens (5th century B.C.),
the Meton cycle. It has the consequence that the moon phases practically repeat after 19 earth revolutions around the sun or after 19 years. That is - illustratively speaking - the background for the effect.

its nice to have document for lay persons,but programmers interest in formulas,could be instead in comments?

The source code of EASTER.ASM is part of the ZIP archive. The calculations are done by the procedure EasterDate. I made sure that it was well commented.