I thought picking the date for Easter was easy

[astroron (Ron)]

Picking the date was I thought just so easy, Sunday closest to Full Moon Ect,
Not So.
http://www.rmg.co.uk/explore/astrono...date-of-easter
Quite complicated really
Happy Easter
cheers

[mithrandir (Andrew)]

Ron, since just about everyone has Perl on their computers these days:

#!/usr/bin/perl -w
use POSIX;

$y=($#ARGV>-1)?$ARGV[0]:strftime('%Y',localtime())
  or die("$0: year required\n");

$c = int($y/100);
$n = $y-19*int($y/19);
$k = int(($c-17)/25);
$i = $c-int($c/4)-int(($c-$k)/3)+19*$n+15;
$i = $i-30*int($i/30);
$i = $i-int($i/28)*(1-int($i/28)*int(29/($i+1))*int((21-$n)/11));
$j = $y+int($y/4)+$i+2-$c+int($c/4);
$j = $j-7*int($j/7);
$l = $i-$j;
$m = 3+int(($l+40)/44);
$d = $l+28-31*($m/4);
@when=(0,0,0,$d,$m-1,$y-1900);
print strftime("%Y/%b/%d\n",@when);

or if you install the Date::Easter module:

#!/usr/bin/perl -w
use POSIX;
use Date::Easter;

$y=($#ARGV>-1)?$ARGV[0]:strftime('%Y',localtime())
  or die("$0: year required\n");

($M,$D)=gregorian_easter($y);
@when=(0,0,0,$D,$M-1,$y-1900);
print strftime("%Y/%b/%d gregorian\n",@when);

($M,$D)=julian_easter($y);
@when=(0,0,0,$D,$M-1,$y-1900);
print strftime("%Y/%b/%d julian\n",@when);

($M,$D)=orthodox_easter($y);
@when=(0,0,0,$D,$M-1,$y-1900);
print strftime("%Y/%b/%d orthodox\n",@when);

The first version is probably simpler in C.

[leon]

Ya learn something every day.

Leon

[Barrykgerdes]

I have a calendar. I get a new one every year. It has the dates of Easter, School holidays, other public holidays etc. no need for a computer program.
Besides every day is a holiday for me!

Barry

PS I also have a program in qbasic that can do the same.

[astroron (Ron)]

Originally Posted by mithrandir

Ron, since just about everyone has Perl on their computers these days:

#!/usr/bin/perl -w
use POSIX;

$y=($#ARGV>-1)?$ARGV[0]:strftime('%Y',localtime())
  or die("$0: year required\n");

$c = int($y/100);
$n = $y-19*int($y/19);
$k = int(($c-17)/25);
$i = $c-int($c/4)-int(($c-$k)/3)+19*$n+15;
$i = $i-30*int($i/30);
$i = $i-int($i/28)*(1-int($i/28)*int(29/($i+1))*int((21-$n)/11));
$j = $y+int($y/4)+$i+2-$c+int($c/4);
$j = $j-7*int($j/7);
$l = $i-$j;
$m = 3+int(($l+40)/44);
$d = $l+28-31*($m/4);
@when=(0,0,0,$d,$m-1,$y-1900);
print strftime("%Y/%b/%d\n",@when);

or if you install the Date::Easter module:

#!/usr/bin/perl -w
use POSIX;
use Date::Easter;

$y=($#ARGV>-1)?$ARGV[0]:strftime('%Y',localtime())
  or die("$0: year required\n");

($M,$D)=gregorian_easter($y);
@when=(0,0,0,$D,$M-1,$y-1900);
print strftime("%Y/%b/%d gregorian\n",@when);

($M,$D)=julian_easter($y);
@when=(0,0,0,$D,$M-1,$y-1900);
print strftime("%Y/%b/%d julian\n",@when);

($M,$D)=orthodox_easter($y);
@when=(0,0,0,$D,$M-1,$y-1900);
print strftime("%Y/%b/%d orthodox\n",@when);

The first version is probably simpler in C.

I wouldn't know where to start, I don't understand any of that stuff
Cheers

[xstream (John)]

Originally Posted by astroron

I wouldn't know where to start, I don't understand any of that stuff
Cheers

It's easy Ron!

Perl 1, Knit 2.

[astroron (Ron)]

Originally Posted by xstream

It's easy Ron!

Perl 1, Knit 2.

Cheers Alex

[skysurfer]

And here the Javascript implementation:

 /**
  * @param year   the year of which easter has to be calculated
  * @param option calculate other date than easter (offset in days)
  * @returns JD of Easter date
  */

function easter(year, option)
{
    var golden, solar, lunar, pfm, dom, tmp, easterday,d;

    /* the Golden number */
    golden = (year % 19) + 1;

    if ( year <= 1752 )
    {
        /* JULIAN CALENDAR */
        /* the "Dominical number" - finding a Sunday */
        dom = (year + Math.floor(year/4) + 5) % 7;
        if (dom < 0) dom += 7;

        /* uncorrected date of the Paschal full moon */
        pfm = (3 - (11*golden) - 7) % 30;
        if (pfm < 0) pfm += 30;
    }
    else
    {
        /* GREGORIAN CALENDAR */
        /* the "Dominical number" - finding a Sunday */
        dom = (year + Math.floor(year/4) - Math.floor(year/100) + Math.floor(year/400)) % 7;
        if (dom < 0) dom += 7;

        /* the solar and lunar corrections */
        solar = Math.floor((year-1600)/100) - Math.floor((year-1600)/400);
        lunar = Math.floor((Math.floor((year-1400) / 100) * 8) / 25);

        /* uncorrected date of the Paschal full moon */
        pfm = (3 - (11*golden) + solar - lunar) % 30;
        if (pfm < 0) pfm += 30;
    }

    /* corrected date of the Paschal full moon - days after 21st March */
    if ((pfm == 29) || (pfm == 28 && golden > 11))
      pfm--;

    tmp = (4-pfm-dom) % 7;
    if (tmp < 0) tmp += 7;

    /* easterday as the number of days after 21st March */
    easterday = pfm + tmp + 1;

//alert(year + ' ' + tmp + ' ' + easterday);

    if (easterday < 11)
        d = datetojd(new Array(year,3, easterday+21,12,0,0));
    else
        d = datetojd(new Array(year,4, easterday-10,12,0,0));
    if (arguments.count > 1)
      d += option;
    d = Math.floor(d);
    return d;
}


function datetojd(datestr)
{
  n = datestr;  // array assumed y-m-d-h-i-s
  var date = new Date(n[0],n[1]-1, n[2], n[3], n[4], n[5]);
   var jd = date.getTime()/86400000 + 2440588 - (date.getTimezoneOffset()/1440);
//alert(jd + ' ' + (date.getTime()/86400000 + 2440588));
   return jd;
}

[mithrandir (Andrew)]

One C++ source for easter is part of lunar.zip from Project Pluto

It compiles, with its driver test program, by:
*nix/cygwin: g++ -DTEST_CODE -o easter easter.cpp
MSVC: cl -DTEST_CODE -o easter.exe easter.cpp

Now, who has it in Java, Pascal, REXX, Python, ...

[ballaratdragons (Ken)]

This thread make absolutely no sense to me.

Must be a foreign language.

Don't worry Ron, you aren't alone in the confusion

[Ric]

It is interesting how it is worked out.

I understand a bit of that code but it's all a bit above me.

[von Tom (Tom)]

A Perl of wisdom from Andrew there...
Anyone got it in BASIC?