This post is part of a series about solving Project Euler problems. This is the post about Problem #19.
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 divisibly 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)?
This problem requires looking at the 1st of the month for every month of the 20th century. This is complicated by variant month lengths, especially Februaries. The native time objects in computer languages only track time starting at midnight on 1970 Jan 1, which complicates looking at any dates prior to that time.