Much is made of the lunar calendar's fine attempt to approximate 365.2425-day Gregorian years. It doesn't do this! It uses 365-day years
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Replying to @qntm
Just subtracting all the leap days out of the Gregorian calendar makes converting to the lunar calendar unimaginably simpler
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Replying to @qntm
Then there are epacts. Epacts require big, horrible, impermanent tables both to compute and to interpret. They are also absolutely unneeded
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Replying to @qntm
The epact of any given year is the "age of the moon [i.e. day of the lunar month] on 1 January". But sometimes it's 30 when it should be 29
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Replying to @qntm
The epact goes up by 11 every year, mod 30. But not always! It also doesn't tell you WHICH lunar month it is
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Replying to @qntm
Basically the epact is a highly complex derived property from a relatively simpler underlying lunar calendar
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Replying to @qntm
And understanding epacts just makes the underlying structure of the Metonic cycle seem unapproachable
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Replying to @qntm
Now here's the thing. I'm not a historian, so this is second-hand, but from what I understand this IS deliberate obfuscation by the Church
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Replying to @qntm
Making Easter difficult to compute makes you reliant on the Church's calculations to know when your feast days should be celebrated
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Replying to @qntm
Anyway, once you've stripped out the leap days from the Gregorian calendar (doable), the Metonic cycle is just this, repeating forever:pic.twitter.com/5xmN6iJILE
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And once you can convert any Gregorian date to/from a lunar date (i.e. a position in that cycle) (also very doable), Computus becomes simple
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Replying to @qntm
Easter falls on the first Sunday following the "Paschal full Moon".
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Replying to @qntm
The "Paschal full Moon" is the first ecclesiastical full Moon on or after the ecclesiastical Northern Hemisphere spring equinox.
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