Get the date of the vernal equinox for every spring I’ve been alive.
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equinoxDays=Map[DateList[FindAstroEvent["MarchEquinox",#,TimeZone->"GMT"]][[3]]&,Table[DateObject[{y,1,1}],{y,1961,2026}]]
Out[]=
{20,20,21,20,20,20,21,20,20,20,21,20,20,20,21,20,20,20,21,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,19,20,20,20,19,20,20,20,19,20,20}
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Tally[equinoxDays]
Out[]=
{{20,58},{21,5},{19,3}}
Now let’s see if astronomical events match up with the Easter algorithm.
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equinoxes=Map[FindAstroEvent["MarchEquinox",#,TimeZone->"GMT"]&,Table[DateObject[{y,1,1}],{y,1961,2026}]]
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In[]:=
fullMoons=Map[FindAstroEvent["FullMoon",#,TimeZone->"GMT"]&,equinoxes]
Out[]=
In[]:=
easters=Table[ResourceFunction["EasterSunday"][y],{y,1961,2026}]
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,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,
If the algorithm matches astronomy, the following differences shouldn’t be more than a week
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diff=easters-fullMoons
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2019 differed by 31 days. When was its vernal equinox?
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FindAstroEvent["MarchEquinox",DateObject[{2019,1,1}],TimeZone->"GMT"]
Out[]=