I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
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@grb090423 Backwards compatibility. It's tied to a Jewish holiday, and the Jewish lunisolar calendar is built radically differently from the solar-dominant Roman calendars that grew dominant in the Christian parts of Europe.
Thank you for explaining this. I did not know
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@riley Fascinating. If the etymology had taken a different twist I could well be typing this on an Eastering machine. @sundogplanets
@psneeze Yep. Or the Rising Machine.
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@psneeze Yep. Or the Rising Machine.
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Thank you for explaining this. I did not know
@grb090423 You might also find this tidbit intriguing: https://toot.cat/@riley/116249726406937771 @sundogplanets
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RE: https://telescoper.blog/2026/04/03/finding-easter/
I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
I had absolutely no idea how complicated the date of Easter is. Wow.
to be fair, all things Catholic are complicated
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@grb090423 You might also find this tidbit intriguing: https://toot.cat/@riley/116249726406937771 @sundogplanets
I did. Thanks!
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@grb090423 You might also find this tidbit intriguing: https://toot.cat/@riley/116249726406937771 @sundogplanets
@grb090423 In the early days of the Christianity, the Easter date could be determined in Rome, and just, effectively, mailed to wherever there were Christian congregations. But by the late 400s / early 500s, the Roman Empire was in such a delapidated state that reliable mailing started to be an increasing problem, so various offline methods for the Easter determination were considered. The officially adopted one was eventually based on an algorithm developed by one Dionysios Exiguus, or Dennis the Geek, potentially partly because of its another important benefit: it allowed the steps to be unambiguously independently verified, and mistakes caught. (There were a couple of embarrassing mistakes in some Easter tables that the early Popes published. Big scandals in their days, because holidays were Serious Business. Literally.)
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@grb090423 In the early days of the Christianity, the Easter date could be determined in Rome, and just, effectively, mailed to wherever there were Christian congregations. But by the late 400s / early 500s, the Roman Empire was in such a delapidated state that reliable mailing started to be an increasing problem, so various offline methods for the Easter determination were considered. The officially adopted one was eventually based on an algorithm developed by one Dionysios Exiguus, or Dennis the Geek, potentially partly because of its another important benefit: it allowed the steps to be unambiguously independently verified, and mistakes caught. (There were a couple of embarrassing mistakes in some Easter tables that the early Popes published. Big scandals in their days, because holidays were Serious Business. Literally.)
You are educating me! I can definitely say TIL.
Dennis the geek... Is that real?!
Do you know so much about this because you have studied it?
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RE: https://telescoper.blog/2026/04/03/finding-easter/
I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
I had absolutely no idea how complicated the date of Easter is. Wow.
Thanks for illuminating this!
I remembered from childhood education that the date of Easter was determined by some mysterious calculus, performed in some faraway place by some select cognoscenti using some ancient methodology that little boys in the backwoods of North Carolina will never be able to master. I also learned that I should not waste time on things I can't influence and don't care enough to understand. Now I just look at the calendar and the problem is solved!
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You are educating me! I can definitely say TIL.
Dennis the geek... Is that real?!
Do you know so much about this because you have studied it?
It's sort-of real.
Dionysios was once a popular Greek name, derived from the name of the ancient Greek deity of drinking and being merry. The modern English Dennis is an adaptation of it, the same way a lot of modern English names are adaptations of Greek names poularised by Christianity's spread. This particular Dionysios was a monk known for being small and humble ('Exiguus' literally means 'Humble'), and, well, also for enjoying computing things. Hence, I submit that 'the Geek' is a defensible translation of his Greek nickname.
I know these things because Knuth's The Art of Computer Programming includes a passage about the Computus, as an example of an early elaborate algorithm, and, being an #ADHD kid, I promptly descended into the rabbit-hole.
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@grb090423 In the early days of the Christianity, the Easter date could be determined in Rome, and just, effectively, mailed to wherever there were Christian congregations. But by the late 400s / early 500s, the Roman Empire was in such a delapidated state that reliable mailing started to be an increasing problem, so various offline methods for the Easter determination were considered. The officially adopted one was eventually based on an algorithm developed by one Dionysios Exiguus, or Dennis the Geek, potentially partly because of its another important benefit: it allowed the steps to be unambiguously independently verified, and mistakes caught. (There were a couple of embarrassing mistakes in some Easter tables that the early Popes published. Big scandals in their days, because holidays were Serious Business. Literally.)
@riley @grb090423 @sundogplanets I didn't know he was called Dennis (sorry).
Anyway, thanks for sharing.
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It's sort-of real.
Dionysios was once a popular Greek name, derived from the name of the ancient Greek deity of drinking and being merry. The modern English Dennis is an adaptation of it, the same way a lot of modern English names are adaptations of Greek names poularised by Christianity's spread. This particular Dionysios was a monk known for being small and humble ('Exiguus' literally means 'Humble'), and, well, also for enjoying computing things. Hence, I submit that 'the Geek' is a defensible translation of his Greek nickname.
I know these things because Knuth's The Art of Computer Programming includes a passage about the Computus, as an example of an early elaborate algorithm, and, being an #ADHD kid, I promptly descended into the rabbit-hole.
This is great!
And I agree, Dennis the Geek should absolutely be accepted
Thanks so much for widening my knowledge today! I didn't know any of this
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RE: https://telescoper.blog/2026/04/03/finding-easter/
I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
I had absolutely no idea how complicated the date of Easter is. Wow.
@sundogplanets The date. The bunnies. The eggs. The rising from the dead. It would be a challenge to make Easter less Christian than it already is.
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RE: https://telescoper.blog/2026/04/03/finding-easter/
I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
I had absolutely no idea how complicated the date of Easter is. Wow.
@sundogplanets What shocks me most of all is how the dude was born at Christmas and they nailed him to a cross 4 months later.
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RE: https://telescoper.blog/2026/04/03/finding-easter/
I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
I had absolutely no idea how complicated the date of Easter is. Wow.
@sundogplanets first sunday after first full moon after 25th march ... Easter is a holy day for procrastinators
I'm not religious either, I think I learned that in my 40s -
@grb090423 Backwards compatibility. It's tied to a Jewish holiday, and the Jewish lunisolar calendar is built radically differently from the solar-dominant Roman calendars that grew dominant in the Christian parts of Europe.
@riley @grb090423 @sundogplanets
Though it doesn't always (nearly) coincide with Pesach.
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@sundogplanets What shocks me most of all is how the dude was born at Christmas and they nailed him to a cross 4 months later.
@rozeboosje
Growth hormones /j
@sundogplanets -
@rozeboosje
Growth hormones /j
@sundogplanets -
Thanks for illuminating this!
I remembered from childhood education that the date of Easter was determined by some mysterious calculus, performed in some faraway place by some select cognoscenti using some ancient methodology that little boys in the backwoods of North Carolina will never be able to master. I also learned that I should not waste time on things I can't influence and don't care enough to understand. Now I just look at the calendar and the problem is solved!
@oldclumsy_nowmad @sundogplanets My grandmother had something called the Book of Common Prayer (Church of England) and it was all spelled out in the back of there.
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RE: https://telescoper.blog/2026/04/03/finding-easter/
I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
I had absolutely no idea how complicated the date of Easter is. Wow.
@sundogplanets Hilda of Whitby says "hold my beer"
"Bede present[s] the synod as a victory for the Roman party...[but doubted their use in Rome]. He produced his own version based on the Alexandrian tables, as amended by Dionysius...in his De Temporibus (703) and in more detail in his De Temporum Ratione (716–25). The Bedan tables came to be accepted in the British Isles and the Carolingian Empire in the ninth century and in Rome in the tenth."
https://en.wikipedia.org/wiki/Synod_of_Whitby
Yes! 
