title: How many Sundays fell on the first of the month during the twentieth century?
url: http://projecteuler.net/problem=19

desc: |
  You are given the following information, but you may prefer to do some research for yourself.
  1 Jan 1900 was a Monday.
  Thirty days has September,
  April, June and November.
  All the rest have thirty-one,
  Saving February alone,
  Which has twenty-eight, rain or shine.
  And on leap years, twenty-nine.
  A leap year occurs on any year evenly divisible by 4, but not on a century unless it is divisible by 400.
  How many Sundays fell on the first of the month during the twentieth century (1 Jan 1901 to 31 Dec 2000)?

  
solution: Instead of using buildtin DateTime language features this use a homemade algorithm

solutions:
  solve.php:
    desc: Basic solution
    language: php
  solve.rb:
    desc: Basic solution
    language: ruby