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Doomsday Calculator - Calculate the weekday of any date in your Head

This calculator gives a quick lesson on how to calculate the weekday of any given date without the help of calculators, computers, or calendars is using the doomsday algorithm.

Enter the date to calculate

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1) How many times does the number 12 fit as a whole into the two last digits of the year number?

Last two year digits: 83

12 fits in 6 time(s)

2) What is the difference between the two last digits of the year number and the product of the multiples of 12 from calculation 1 (remainder)?

Last two year digits: 83

12 times Step 1: 12 x 6 = 72

83 - 72 = 11

3) How many times does the number 4 fit into the result of calculation 2?

Result from last step: 11

4 fits in : 2 time(s)

4) What is the century's anchor day?

  • 1800-1899 - Friday (5)
  • 1900-1999 - Wednesday (3)
  • 2000-2999 - Tuesday (2)
  • 2100-2199 - Sunday (0)

5) Add up all the results.

6 + 11 + 2 + 3 = 22

6) Subtract whole multiples of 7 from the result of calculation 5.

This will result in a number between 0 and 6, which corresponds to the doomsday of the year.

22 - 7 = 15
15 - 7 = 8
8 - 7 = 1
  • 0 - Sunday
  • 1 - Monday
  • 2 - Tuesday
  • 3 - Wednesday
  • 4 - Thursday
  • 5 - Friday
  • 6 - Saturday

7) Find the closest doomsday.

Note: the year specified is a leap year.

  • January 34
  • February 2829
  • April 4
  • May 9
  • June 6
  • July 11
  • August 8
  • September 5
  • October 10
  • November 7
  • December 12

8) Count forward/backward from the doomsday to the specified date.

  • 04 April 1983 - Monday
  • 11 April 1983 - Monday
  • 18 April 1983 - Monday
  • 19 April 1983 - Tuesday
  • 20 April 1983 - Wednesday

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