Enter any date, and find out what day of the week it would be using the Doomsday Rule!
Please enter a year (1+)
Please enter a month (1-12)
Please enter a day (1-31)
Enter any date, and find out what day of the week it would be using the Doomsday Rule!
Please enter a year (1+)
Please enter a month (1-12)
Please enter a day (1-31)
The Doomsday Rule is an algorithm created by John Conway for calculating the day of the week of any day in history or the future.
There are a few principles which make these calculations possible. There are patterns in the cycle of days in the week over the course of months, years, decades and even centuries.
For example, there are approximately 5,217.86 weeks in a century. This means that every 100 years, the same date will be a numerically different day of the week by a roughly constant amount.
This means that 28/2/2100 will be a tuesday, 28/2/2200 will be a Thursday, and 28/2/2300 will be a Saturday - a difference of two days each time.
These cycles allow us to calculate what day of the week any date will be - you can even do it in your head!