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Calculating the Date of Easter

The God Plays Dice blog has an entertaining post on how the date of Easter is calculated. Wikipedia has all the messy details of course, but the blog makes a good introduction to the topic. "Easter is the date of the first Sunday after the first full moon on or after March 21... [T]he cycle of Easter dates repeat themselves every 5,700,000 years. The cycle of epacts (which encode the date of the full moon) in the Julian calendar repeat every nineteen years. There are two corrections made to the epact, each of which depend[s] only on the century; one repeats (modulo 30, which is what matters) every 120 centuries, the other every 375 centuries, so the [p]air of them repeat every 300,000 years. The days of the week are on a 400-year cycle, which doesn't matter because that's a factor of 300,000. So the Easter cycle has length the least common multiple of 19 and 300,000, which is 5,700,000 [years]."

16 of 336 comments (clear)

  1. how is it... by MousePotato · · Score: 2, Insightful

    This is not a science article. Arguably it is a math article to the interested christians on /. but certainly not science.

    1. Re:how is it... by Otter · · Score: 4, Insightful

      Your grasp of astronomical chronology far exceeds mine, then. I'm not a Christian and have no interest in the holiday per se, but thought this article was a fascinating piece of science history, and certainly learned more science from the underlying astronomy and the computation thereof than I would have gotten from any ten Roland Piquepaille rehashings of press releases he doesn't understand.

  2. Re:Why would by sonicdevo · · Score: 4, Insightful

    Just because the date (and what it commemorates) is meaningless to you, is it really necessary to cast all those who do care about it as irrational?

  3. Pope decides by iknownuttin · · Score: 3, Insightful
    I find it quite amusing that the birth of Jesus is pretty much set in stone (at least if I believe that day to be Christmas), but the date of his death (or resurrection) isn't.

    The date of birth of Jesus was also pulled out of the ass of some Pope. Christian Holidays were set on their particular dates to get medieval folks to stop their 'pagan' rituals and instead celebrate Christian rituals. Christmas:Winter solstice Easter:Beginning of Spring (Ostara now for you Wicans). I'm such a lapsed Catholic I can't remember the Holy days for other celestial events.

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  4. Re:Why would by britneys+9th+husband · · Score: 3, Insightful

    Because they run a grocery store and need to know when to stock the chocolate bunnies and egg dyeing kits

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  5. Re:Why would by Breakfast+Pants · · Score: 4, Insightful

    Do you ever cast UFO believers as irrational?

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    WHO ATE MY BREAKFAST PANTS?
  6. Easter Island by drquoz · · Score: 2, Insightful

    Could this be the solution to the mystery of Rapa Nui?

  7. Annual celebrations are arbitrary anyway. by raehl · · Score: 4, Insightful

    Yes, it's set in stone on the wrong date.

    Right. Because we have to celebrate everything in exact intervals of one earth-sun-revolution, and only whole-number interval offsets from the time of the original event.

    There's no such thing as the 'right' and 'wrong' date. An event happens. Choosing to celebrate that event once a year (where "year" is the amount of time it takes the earth to go around the sun once) is arbitrary in the first place. It would be just as 'right' to celebrate it every 12 moon-earth revolutions, or 2 mercury-sun revolutions.

    If you're already going to base your celebration intervals on the convenience of how often one ball of rock revolves around one ball of gas because you happen to live on said ball of rock, you might as well always celebrate something on the 259th day of the year, or the 4th time the 4th day of the week falls in the 11th month of the year, or the 1st 7th day of the week following the vernal equinox.

    Getting bent out of shape because the commemoration/celebration of an event doesn't have the same calendar date as the original event - especially when the original event occured in a time period where the calendar you're using didn't even exist - seems pretty silly. Especially when you're celebrating the birth/death of the son of God.

  8. Re:In Perl by gimpeh · · Score: 1, Insightful

    That is not nearly confusing enough. The original alogrithm was clear and concise. Your Perl implementation should therefore cause distress and confusion. You're a shame to the profession.

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    Script kiddies ate my sig.
  9. Good Grief it's all wrong anyway. by psychosmyth · · Score: 2, Insightful

    Every day is Easter! People like to kill Christ over and over and then make the point of reminding us in detail of the crucifiction over and over. It happened once and He lives now and forever. The Church has a habit of missing the point of much of God's Word and this puts Christians in a position to be taunted,contradicted and mis-led. I do celebrate Christian holidays but more low-key. Christians are to celebrate Christ 24/7/365. I do think it's neat how this formula was derived though and I'd rather see that as the topic here than see negative comments about Easter. A true Christian would not dare insult Islam or Judeism or any other religion but offer to share Christ's teachings instead. Please be respectful or the mod-man will stike.

  10. Re: Thinking fundies ?? by psychodelicacy · · Score: 2, Insightful

    I disagree. Science tells us that, if we don't eat in a certain way, we will die prematurely. It tells us that we must recycle more plastic in order to save the planet. It tells us that the cure for depression is medication. And when we've done all those things (because we'd be stupid, lazy, immoral if we didn't) a whole new lot of science comes along and proves that the opposite is true.

    A good scientific education may teach you how to think, but for most people science is something that dictates government policy, legislation, and lifestyle choices without their actually having to understand any of the details or processes. For most people, science becomes a faith. I'd bet that the average American or Briton does more things based on the latest scientific evidence than s/he does based on religious belief.

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  11. Re:Which explains why it is plain silly! by sumdumass · · Score: 2, Insightful

    In this case, there happen to be important connections to passover and Christ's death and resurrection. In other words, it is part of the story plot. A simple day on the calender would remove that connection to a degree that most people wouldn't be comfortable with. Jesus was in town for passover- he was a jew after all.

    The story of Jesus is complicated, especially so when you bring the trinity into it. But the connections to passover would lose it's significance when for the most part passover is still practiced widely. As it is, the rituals and celebrations would become a droned out day with little or no meaning without the connection.

  12. Re:Happy Zombie Jesus Day! by groslyunderpaid · · Score: 2, Insightful

    DISCLAIMER: I am an independant protestant with what is probably an unintended bias.

    *sigh*

    I'm tired of having to go over this with my atheist friends.

    Please. Remember this, if you remember nothing else.

    The term "Zombie Jesus" makes no sense.

    The religious belief is that Jesus "came back from the dead", or "rose from the dead". The angel said "Why seek ye the living among the dead?".

    Zombies, on the other hand, are not living OR dead. They are the undead, which is a different thing entirely.

    You would think since atheists believe both are make believe, they would be able to distinguish among the two.

    Then again maybe the real issue is that most of them don't understand the belief, so most of their comments sound like retardedness to those of us who do believe.

    Case in point: The last time I explained this to an atheist, their response was "Well why didn't he just come back again the 2nd time he died?"

    Really? If you are ignorant enough to be able to make that comment, you are too ignorant to argue against that establishment of religion.

  13. Re:It's not even accurate ... by n6kuy · · Score: 3, Insightful

    > ...same-sex activity is normal for many mammals,
    > contrary to the ignorant ramblings preached from pulpits every weekend.

    You fail Critical Thinking 101.
    You can't get an "ought" from an "is". See http://en.wikipedia.org/wiki/Is-ought_problem
    The fact that certain behaviors among animals can be observed in nature doesn't imply any moral (or amoral) imperative among humans. There are lots of things animals do that no one would consider OK for humans to do.

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    If you disagree with me on social issues, then it's pretty clear that you are a narrow-minded bigot.
  14. Re:Birth and death by hierofalcon · · Score: 3, Insightful

    The date of Christ's death is fixed on the Jewish calendar. There are other comments giving possible actual dates listed here. I personally subscribe to the 15 Nisan 31 CE date (putting the crucifixion on a Wednesday), but I don't have problems with people who prefer 14 Nisan on a different year. Passover always starts with a day of preparation on 14 Nisan, each and every year, followed by the seven day passover feast. If you go through the chronology of the Bible, you'll then come up with a crucifixion on either the day of preparation or Passover itself. This is followed by three days in the grave and a Resurrection on the Jewish first day of the week (any time Saturday sunset to Sunday morning when the tomb was seen to be empty).

    The whole problem is that the Jewish calendar doesn't match up with ours. Its months are based on the lunar cycles and tend to have fixed lengths. In order to keep in sync with the Earth's rotation around the sun, leap days are added as needed and every few years a leap month is added. These are always added at the end of the year. Thus, 15 (or 14) Nisan is always a fixed date on the Jewish calendar since it's in the first month of the year, but it won't match to a fixed date on the Gregorian calendar. Likewise, the day of the Resurrection (three days after His crucifixion) will not always come on a Sunday since Passover moves w.r.t. the Gregorian calendar, which irritated a Bishop back in the early hundreds, and caused the goofy Easter mess in the first place. If you want a modern day parallel, look up Golda Meir's date of death. If you were to commemorate this as a Jew, you'd almost certainly do it on the same date on the Jewish calendar each year. Yet this moves the date on the Gregorian calendar around the same way Passover moves. Last year, it (8 Kislev) would have been November 18 Gregorian. Next year it will be December 5. The year after, it'll be back in November.

    If you're really interested, you should study what the passover was about (instituted long, long before Christ was born), and look at how perfectly it was a type of Christ's death. It's really fantastic. Even the actual Jewish passover rituals are a type of Christ's death, burial, and resurrection. It's a shame not many Jews have really seen that yet. The next passover, when He returns for His church in the air will be just as great an event. We don't know when that will be, but many of the Christian "big events" (Christ's birth, Christ's death, the initial outpouring of the Holy Spirit) have occurred at the times of established Jewish festivals.

    I tend to agree that we should celebrate Christ all the time and not just on one day, but I'd like to see it move to be in sync with passover, regardless of whether that happened to put it on a Sunday or not on the Gregorian calendar. They ought to get Maundy Thursday and Good Friday corrected while they're at it.

    And yes, the December 25th birth date is just as goofy - both for reasons of a fixed Jewish calendar date never being fixed on the Gregorian calendar, and for it needing to be tied to the Feast of Tabernacles which is much earlier in the year (15 Tishri). A good bet for a birth date would be October 4, BC 4 (Tishri 15, 3757) according to some sources.

    Getting bogged down in debates over dates obscures the most important facts. He was crucified to provide a holy sacrifice for our sin. He bore stripes for our healing. Roman guards were posted to guard the tomb under penalty of death if anything happened to the body. They didn't count on angels showing up and rolling away the covering rock (not that Christ needed angels help - that was for the benefit of the people who would come). He arose, just as He said He would after three days. He arose with keys to the death and the grave, and led those righteous souls who were being kept under Satan's control in the grave to heaven. He appeared bodily to hundreds after that point in time (and at the time of His resurrection, many others who had died were also seen in Jerusalem before going to Heaven). He is reigning on the right hand of God. At some point, God will send Him to gather up His church. You don't want to miss that time.

  15. Re:Metric School Terms by drew · · Score: 2, Insightful

    Interesting - I always assumed that "choosing" the date of Easter was a simple and fairly straightforward affair - it should always be the Sunday following the Jewish passover feast. How the date for that is determined, I am not really sure off the top of my head, but it doesn't seem like it should have been that hard to figure out for any Christian leader who was particularly interested, since the Christians included most of the Jewish scriptures and proscriptions in their own.

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