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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]."
"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
In the UK school is split into three terms ... in the middle of each, you get a week off, and between them, you get two weeks off. Except over the summer when it's six weeks.
So there's more holiday through the year, but the summer vacation is shorter.
(This is probably because we don't have as much summer.)
Only problem is, your way isn't always right, because the date of Easter is always calculated from March 21st even if (as this year) the northern hemisphere spring equinox doesn't fall on that date.
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;
Absolutely - the Anglo-Saxons had a lot to say about the dating of Easter. See http://faculty.virginia.edu/OldEnglish/aelfric/detemp.html for an original text on the subject if you're wildly interested. Melvyn Bragg's novel "Credo" dramatises the Synod of Whitby and gives a sense of exactly how serious an issue this was for people. Since Easter is the major Christian feast, it was a matter of orthodoxy to date it correctly. Interesting to think that being bad at math could make you a heretic!
A closed mouth gathers no foot.
Even worse... there are Christian women on /.
Seriously, do you assume that all Christians are no-brain idiots who think dinosaur skeletons are an atheist conspiracy? Donald Knuth is a Lutheran, Gregor Mendel was an Augustinian monk, Copernicus was a priest, as was Georges Lemaitre. Lord Kelvin and Max Planck were committed Christians, Arthur Stanley Eddington was a Quaker... There are more here: http://en.wikipedia.org/wiki/List_of_Christian_thinkers_in_science (Not all of those in this list were Christians throughout their lives, but the ones I've named were/are.)
A closed mouth gathers no foot.