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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]."
In the UK the academic year is split according to the date of Easter. I recall hearing about an effort to move to a "metric" system which doesn't depend on Easter. This suddenly makes a lot of sense...
This is not a science article. Arguably it is a math article to the interested christians on /. but certainly not science.
Prospecting Stinks. Stop Wasting Time on Cold Calling.
I've always thought that it is more fun to say the date of Easter is "the first Sunday after the first full moon after the Spring Equinox," rather than March 21st.
It sounds so much more Pagan my way.
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?
Historical significance, for one. The history of time-keeping and astronomy are intimately tied to the need to celebrate religious events; this goes back much before Christianity. It's really a very neat subject, and it's really fascinating how much math developed simply out of a need to know when and how to throw a party for the gods.
"Easter is termed a moveable feast because it is not fixed in relation to the civil calendar. Easter falls at some point between late March and late April each year (early April to early May in Eastern Christianity), following the cycle of the moon. After several centuries of disagreement, all churches accepted the computation of the Alexandrian Church (now the Coptic Church) that Easter is the first Sunday after the first fourteenth day of the moon (the Paschal Full Moon) that is on or after the ecclesiastical vernal equinox. Easter is linked to the Jewish Passover not only for much of its symbolism but also for its position in the calendar. The Last Supper shared by Jesus and his disciples before his crucifixion is generally thought of as a Passover meal, based on the chronology in the Synoptic Gospels..."
http://en.wikipedia.org/wiki/EasterWikipedia
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.
I prefer Flambe as apposed flamebait.
The same, except they use the Julian calendar where the western Christian churches use the Gregorian calendar. The calculation of the Jewish passover uses actual observations of the moon so that may be different again.
You'll find it all on Wikepedia.
Because they run a grocery store and need to know when to stock the chocolate bunnies and egg dyeing kits
Hear recorded Slashdot headlines on your phone! New service beta testing. Just call (248) 434-5508
Do you ever cast UFO believers as irrational?
--
WHO ATE MY BREAKFAST PANTS?
Agreed, the history of time-keeping is a very interesting and important subject, however, an arcane method of determining the date for a specific holiday belongs in the category of 'curious minutiae' and is in and of it self just an obscure exercise, except for the devout adherents to it's attending myths.
In his defense, the picture tagged with the story is pi.
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.
Yes, it's set in stone on the wrong date. Shepherds were living outside with their flocks when Jesus was born, yet they wouldn't be doing this in December. It's too cold in Israel. In addition, Jesus died on Nisan 14 (the first full moon after the vernal equinox)... not on a Friday year after year.
"Nature doesn't care how smart you are. You can still be wrong." - Richard Feynman
I seriously doubt that Mary went around saying that she became pregnant despite being a virgin, for two reasons. First, everyone would have read between the lines and assumed Jesus was the product of infidelity, then as now. Saying that Yahweh was the real father makes you look like you're not just loose, you're also batshit insane. The cover story would have been that Joseph was the father.
What's far more likely is that the virgin birth is a later addition to the story of Jesus. In comic book terminology, this is a retroactive alteration of the continuity, or "retcon". "Hm... how do we explain the origin of Jesus' amazing superpowers? How is he able to walk on water, cure leprosy, and feed multitudes using a single loaf of bread, if he's just some average Jew? It's just not plausible, our audience will never buy it. I KNOW! We have a special "Origins of Jesus" issue in the Bible, where we reveal that ACTUALLY, Jesus is the son of God! Now, the fact that he has these amazing superpowers makes sense!"
It's exactly like how Marvel went back and created a backstory to explain the origins of the super-powers of the X-men. In the case of Marvel, alien visitors altered the DNA of ancient humans which resulted in mutants like Wolverine. In the case of the Catholic Church, a super-powerful being impregnates Jesus' mom. It's a really ancient theme. If you recall many of Greek heroes, such as Hercules, had gods for parents, which explained why they were so powerful. Achilles was more like the Incredible Hulk, in that exposure to magic (the waters of the River Styx in the case of Achilles, gamma rays in the case of the Hulk) give them their powers. But Odysseus is like Batman- he doesn't have any superpowers, he's just clever.
Ah! The March of progress.
Next year it will be April again though.
paintball
Could this be the solution to the mystery of Rapa Nui?
I don't care about the myths - the chocolate bunnies and eggs are good enough for me.
Save the earth! It is the *only* planet with chocolate!
Excuse me, but please get off my Pennisetum Clandestinum, eh!
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.
paintball
sub GetEasterDate {
my($year)=@_;
# http://www.smart.net/~mmontes/nature1876.html
my $a=$year%19;
my $b=int($year/100);
my $c=$year%100;
my $d=int($b/4);
my $e=$b%4;
my $f=int(($b+8)/25);
my $g=int(($b-$f+1)/3);
my $h=(19*$a+$b-$d-$g+15)%30;
my $i=int($c/4);
my $k=$c%4;
my $l=(32+2*$e+2*$i-$h-$k)%7;
my $m=int(($a+11*$h+22*$l)/451);
my $month=int(($h+$l-7*$m+114)/31);
my $p=($h+$l-7*$m+114)%31;
my $day=$p+1;
return (0,0,0,$day,$month-1,$year-1900);
};
$x='S24;r)>63/* h@<5+oZ)32"5cz';$me='phroggy'x$];
$x=~y+ -xz+\0-Tx+;print$_^chop$me for split'',$x;
Only valid between 1583 and 4899
function! s:EasterSunday(year, return_value)
if a:year 4089
return 0
endif
let a = a:year / 100
let b = a:year % 100
let c = (3 * (a + 25)) / 4
let d = (3 * (a + 25)) % 4
let e = (8 * (a + 11)) / 25
let f = (5 * a + b) % 19
let g = (19 * f + c - e) % 30
let h = (f + 11 * g) / 319
let j = (60 * (5 - d) + b) / 4
let k = (60 * (5 - d) + b) % 4
let m = ( 2 * j - k - g + h) % 7
let n = ( g - h + m + 114) / 31
let p = ( g - h + m + 114) % 31
if a:return_value == 1
let easterday = p + 1
return easterday
else
let eastermonth = n
return eastermonth
endif
endfunction
Is it just me or does it seem like anything posted having to do with politics or religion turns into a mod point black hole?
The game.
In my part of the world the Monday after Easter is a national holiday. I've actually implemented the Gaus algorithm to compute the date of Easter in multiple programs, to check if people working on a given date were entitled to extra compensation for working on a holiday.
I won't hesitate to recommend the book 'Marking Time' by Duncan Steel - it's a great book about the history and evolution of calendars. The date of easter is a particularly interesting question and Duncan goes as far as to explain how the date of Easter was at the core of an English plan to attack the legitimacy of the Catholic church and how this plan was what triggered Britain's first attempts to colonize America, great stuff.
Calendars are funny things.
Those who fail to understand communication protocols, are doomed to repeat them over port 80.
I'm actually worried that in 500 years or so, FSM will be the dominant religion. :)
Just because I'm curious : where does it say that (not that it changes anything about the meaning of the bible if it does indeed say that, but I'm curious nonetheless) ?
... (I'm sure you can fill this in, this seems to be a smaller group though)
Besides, religion isn't irrational : this article gives a few hints on why (note : if you know a bit of stuff about the differences between religions you'll find that while the arguments presented are not about one single religion, they do exclude a lot of religions, in short the article makes a lot of sense when interpreted to a christian context, and specifically compares this christian(-oriented*) belief system to atheism, it states that atheist societies exist for about 20 years while christian communities generally survive for 150 years, with a number of them being older than any reliable records (about 200 years that is))
* -oriented because of 2 facts :
1) some members of other religions are "cryptochristian", ie they believe and practice the principles of christianity, even when in direct contradiction with their stated religion
2) some christians
Of course, when these calculations consider the addition of the Easter Bunny, the Fibonacci sequence, represented as an infinite mathematical set, must be applied to the cycle result. In the end you'll find it's bunnies all the way down.
now, does all that fancy mathematics and statements about the repetition cycle of days include the Leap Year's Lead Day, as well as the fact that it didn't exist the last time this cycle started?
Yes, the formula by Gauß does. That's one of the reasons the mathematics have to be so fancy.
the way he would have had to if this were a Muslim story
Or, you know, a Jewish or Christian one. The penalty of death by stoning for adultery is straight out of the Old Testament.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
Ironically you're trying to show the illogical nature of one who professes to dislike Fundamentalists (presumably because of their illogical nature).
... I don't think that word means what you think it means."
Of course, the person in question probably has no idea where the term Fundamentalist comes from in modern Christian terms, so their Worldview on the issue is most likely to be entirely based in the media. Yes, the very media from which science should not be learned either.
Or, "Fundamentalism
- Michael T. Babcock (Yes, I blog)
There are millions of people who did not celebrate Easter today (23 March 2008) because they will be celebrating on 27 April 2008 (yep, 5 weeks later ... this is an unusual year). Orthodox Easter is computed to always fall after Passover (because, recall, the Last Supper was a Passover Seder).
Here's a web site that is more, um, shall we say, enlightened: http://www.assa.org.au/edm.html
One of the main differences between the calculations for Roman Catholic Easter and Eastern Orthodox Easter is in which calendar (Gregorian or Julian) is used. Use Google. It's actually quite interesting because of all the history and politics involved. It's not just simple (eg, exactly when is the moon full? over which point on the earth?) as one might think.
Put my fist through my alarm clock with its ding-dong death inside my ear. - The Blackjacks.
If you want to say that Passover's date is set at spring pagan holiday time, you'll need to argue with your rabbi or maybe Lehrhaus Judaica about whether your druids are at all the same kinds of pagans as Caananites were. And if you want to say that the name "Easter" and the bunnies and and eggs and marshmallow chickens are ripped off from Germanic spring fertility goddess stuff, you'll have a tough time getting anybody to argue the other side except maybe some atheists who'll say that the Germanic fertility goddess folks ripped that off from nature, which provided the bunnies and eggs, or from the chemical industry who brought us marshmallow peeps.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
$unixdatenum = easter_date($year);
"Enjoy what you're doing! If it becomes drudgery, you're doing it wrong!" - Jim Butterfield
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.
The date IS fixed -- it's all a matter of perspective. Dates are divisions of a calendar, and a calendar tracks time using periodic and regular astronomical events. Obviously, the easiest of these is the day, since it's easy to tell when the sun rises, and our body clocks (and therefore the work day) are tuned to it. Unfortunately, days are too granular: to really organize a civilization, you need larger logical units (such as weeks, months and years). Nowadays, we use a calendar which tracks the sidereal year -- the time it takes for the earth to complete one full orbit. For agricultural purposes, this is ideal, since it will tell you when to grow your crops. Unfortunately, it was a tricky one to calculate: even if you know that the earth orbits the sun, you're stuck dealing with the fact that the orbit is nearly circular so you can't find a visible difference in size in the sun, and the stars are so incredibly distant that there's no appreciable parallax. One cue that you CAN watch for is the equinox, and this is exactly what early calendars did to track the seasons. Your typical farmer isn't going to have the time or the tools to measure when the day and night are of equal length, but he can get a general feel for it, and you can have a few people set aside whose job in the springtime is to watch the length of each day.
For the common man, an easier thing to watch is the moon. The phases of the moon are not only regular, but they're highly visible and uncomplicated. This means that if your calendar has something to do with the moon, then it's not only easy for your astronomers to track, but it's easy to explain to the unwashed masses: just tell them the festival is on the next new or full moon, and they'll know exactly what you mean. You can also track days for a very small number of days; 7, for instance. You can tell people "go out and work really hard for 6 days, and on the seventh, take a break," and most people can do that (and those that can't can just notice that those who can aren't working on some days). In the Jewish tradition, as you're probably aware, the seventh day is called the Sabbath, and is considered sacred.
A mix of the two was popular -- the accessibility of the lunar calendar was nice, but the agricultural significance of a sidereal calendar was needed as well. For the Liturgical year, the calendar starts with the first new moon after the spring equinox. This means that there's not even any pretense that the calendar is equivalent to a sidereal year; the orbital period of the moon just isn't any fraction of the orbital period of the earth.
Easter tries to mix the 3 logical units of measurement: the rules are complicated, but it essentially boils down to finding a date which 1) falls on a Sabbath, 2) comes quickly after an equinox and 3) ties into lunar phase. The way they chose was to set it at the first Sabbath following the first full moon following the spring equinox. But, approximations are applied to make it easier to plan: ancient astronomy was amazing for what they had at their disposal, but really very far from perfect. So, since the need to plan out a major annual festival was superior to the need for people to be able to look in the sky and see it get close, approximations were accepted over time. The "full moon" was assumed to occur 14 days after the new moon, which was in turn predicted from tables generated using an agreed-upon system of reckoning. The equinox was eventually taken to occur on March 21. The end result is that it no longer actually directly corresponds to an equinox or a lunar phase, and is instead based off of approximations that were chosen to make the date easier to work with. Nowadays, the approximation that most proponents of Easter date reform put forth is just to pick something like the first Sunday of April and use that. Others want to go back to a pure lunisolar basis and throw out the approximations. At this point, however, there's not much motivation to do either: we can compute Easter out arbitrarily far now, and it's printed on every c
Yes and no. In the Hebrew Bible, the word used by Isaiah is rightly translated as "young woman." In the Septuagint (the Greek translation of the Hebrew Bible produced nearly 200 years before Christ, and much older than the oldest extant Hebrew language Bible), however, the word is in fact "virgin."
Many Christians themselves, not to mention those who don't know much about the religion (no offense, but the majority of /.), are unaware of the fact that the Apostles themselves would most likely have used the Greek scriptures--indeed, it is apparent throughout the New Testament that the Hebrew scriptures being quoted nearly all are of Septuagintal origin.
To reign is to serve.
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.
A closed mouth gathers no foot.
Copernicus: 1473-1543 Mendel: 1822-1884 Kelvin: 1824-1907 Planck: 1858-1947 Eddington: 1882-1944 Lemaitre: 1894-1966 Knuth: 1938-
So, Copernicus may have been a Christian for the sake of convenience, but I think the others had/have other choices!
A closed mouth gathers no foot.
One still has to take into account what is really going on when the word 'virgin' is used, based on the context of the writing. Even if the translation is literal, a writer might assume that a young woman is 'virginal' when she is, in fact, not. At any given time, not many people have that actual knowledge about an individual, and so it is usually nothing but an assumption, in any time or place. And given the actual record of history, that assumption is probably wrong more often than right.
Whether it is the majority I don't know, but it is certainly many.
You have been substantially misled if that is your understanding. The history of the KJV is somewhat interesting, although I admit to having tired long ago of the debates over its continued and/or exclusive use.
Long story almost criminally shortened, there were problems with the available English translations at the time. In response to complaints to that effect from the clergy, King James proposed, authorized, and funded a project to produce a new interpretation for use in the Church of England. There is no "God told me to fix the Bible" about it, and King James himself took no hand in the translation work. There certainly are controversies and problems around the project, but it was not as you have been lead to believe.
To reign is to serve.
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.
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.
The virgin birth was/is an essential part of the Messianic prophecies of the Jewish people. It derives from Isaiah 7:14:
This passage has been dated to a date prior to the death of Christ in the Dead Sea Scrolls -- somewhere between 335 and 107 BC. So the idea of a virgin birth was well established long before Jesus' actual birth as are many of the miracles that Jesus performed. In fact, if you study the history of the time you will find that there were many others who claimed to be the Messiah and fulfill various prophecies including King Herod himself (the king who killed all of the male babies in Bethlehem in an attempt to end Jesus' life). According to the gospels in the New Testament, Jesus has fulfilled nearly every Messianic prophecy -- far more than any other figure in history.
The only prophecy Jesus has yet to fulfill is the establishment of an eternal government of peace and holiness which Christians believe will occur at his second coming. The fact that he did not fulfill this prophecy is one of the primary reasons that Jews of that day and even today rejected Jesus as their Messiah.
There is a lot more information here to cover than I can possibly relate in a Slashdot post, but there is far, far more to Biblical and Messianic prophecies that you realize. Each miraculous act and many of the statements attributed to Jesus in the New Testament are loaded with meaning and significance to people who understand the Old Testament -- most clearly in the book of Isaiah.
I believe in de-evolution. God made the world perfect, man fell, and its been going downhill ever since!
> ...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.
If you disagree with me on social issues, then it's pretty clear that you are a narrow-minded bigot.
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.
> I always thought it was based on when the Hebrew calendar said the week of Passover was.
It was, originally, and _sort of_ still is.
But over the centuries, as the Jews and Christians codified the rules for their calendars differently, some differences have arisen.
At the time when the Western formula for Easter was set, the Jews tried pretty hard to keep the spring equinox in the first half of the first month (Nisan), so the Easter formula that was established assumes that to be the case -- but the modern Jewish calendar doesn't do that. Arguably, this is a deviation on the Jewish side that takes their calendar out of sync with where it should be.
Additionally, the Western formula for Easter assumes that the Gregorian calendar is always perfectly in sync with the astronomical solar year, and that isn't always necessarily true. (Over long numbers of years it tracks very closely, but in any given year it can be off by a little.) Arguably this is a deviation on the Christian side that takes our calendar out of sync with where it should be -- but in a different way from what the Jewish deviation does.
If we got rid of both deviations and reckoned both calendars in a way that kept them strictly in alignment with the astronomical solar year, then Easter Sunday would always be, if I understand correctly, the Sunday after the Passover Seder.
But the important thing, to my way of thinking, is not the exact date on which the events are celebrated, but the fact that they *are* celebrated. Though the date calculations are interesting. (Then again, I majored in math, so I may define "interesting" differently from some people.)
Cut that out, or I will ship you to Norilsk in a box.