Write the shortest program, in the language of your choice, that takes as input a year on the Hebrew calendar, and outputs the corresponding Gregorian date for Rosh Hashana, in YYYY-MM-DD format.

~$ rh 5771
~$ rh 5772
~$ rh 5773
  • The input may come from either the command line or from stdin, whichever is more convenient.
  • You may assume that the year will be between 5600 (1839) and 6000 (2239), inclusive.
  • 2
    \$\begingroup\$ @trinithis i beg your pardon, dude. the Hebrew calendar was inherited from the Babylonian system of computing ephemerides. this guy figured that out: en.wikipedia.org/wiki/Otto_Neugebauer it is a very cool piece of precognate almagestian mathematics worthy of study by any geek worth his unix pipe \$\endgroup\$
    – ixtmixilix
    Sep 22, 2011 at 22:10

3 Answers 3


Ruby, 192 181 165 characters

$><<Date.jd(347641+e+([h=s%u/19440,84>>e%7+h&1,v=e%7*(374454>>n%19&1-h&s%u/9923),v,n-5765].count 1))

Input is given as a single number on STDIN.

Edit 1: Several arithmetic transformations saved quite a few characters.

Edit 2: There was some room for improvement.


C#, 212

This might seem cheap, but here I go:

using System;using System.Globalization;class P{static void Main(){int y=int.Parse(Console.ReadLine())-5771;var a=new HebrewCalendar().AddYears(new DateTime(2010,9,9),y);Console.Write(a.ToString("yyyy-MM-dd"));}}

with spacing

using System;
using System.Globalization;
class P
    static void Main()
        int y = int.Parse(Console.ReadLine()) - 5771;
        var a = new HebrewCalendar().AddYears(new DateTime(2010, 9, 9), y);
  • \$\begingroup\$ You could save one character by using 5771 as your reference year instead of 5772. \$\endgroup\$
    – dan04
    Sep 19, 2011 at 13:33
  • \$\begingroup\$ @dan04 Done.... \$\endgroup\$ Sep 19, 2011 at 13:36
  • \$\begingroup\$ You shouldn't count Console.Read(); as a part of the program, it's not really needed. \$\endgroup\$
    – user1158
    Sep 20, 2011 at 14:48
  • \$\begingroup\$ @PeterOlson Here's a version at only 190 bytes: using System;class P{static void Main(){Console.Write(new System.Globalization.HebrewCalendar().AddYears(new DateTime(2010,9,9),int.Parse(Console.ReadLine())-5771).ToString("yyyy-MM-dd"));}}. \$\endgroup\$
    – Toothbrush
    Feb 19, 2014 at 17:00

CPAN 5.10, 109

This is even cheaper than the C# solution, for reasons enumerated below. Code first: (character count as a difference to perl -E'' as usual)

$ perl -E'$_="DateTime::Calendar::Hebrew";/:/;eval"require $_";say$`->from_object(object,$_->new(year,<>,month,7))->ymd'
  • steals Peter Olson's idea of just outsourcing it to the library
  • CPAN's current release of DateTime::Calendar::Hebrew doesn't install out of the box, you need to patch it.
  • needs Perl 5.10. No earlier, no later.

At least it's short.


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