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Doomsday Calculator
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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This result is based on the Gregorian calendar and might differ from the actual weekday in some countries.
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
Example Uses
Calculate the day of the week for:
- your birthday
- next Christmas
- a historical event, like the first Moon landing