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The Doomsday rule, Doomsday algorithm or Doomsday method is an algorithm of determination of the day of the week for a given date. It provides a perpetual calendar because the Gregorian calendar moves in cycles of 400 years.
The weekday these dates fall on is called doomsday. The phenomenon is based on the fact that the number of days between these dates are always evenly divisible by 7, which is the number of days per week.
- Step 1: Memorizing Weekdays as Numbers
- Step 2: Memorizing The Anchor Days
- Step 3: Calculating The Doomsday of Any Given Year
- Step 4: Move from The Doomsday to The Date in Question
In Conway's concept, each weekday is represented by a number: Memorize these numbers before moving on. As a mental anchor, it may be helpful to think of Tuesday as “Twosday”.
Calendars repeat themselves every 400 years, so all you need to do is to remember the anchor days for 4 centuries. As most dates you will come across lie in the time span between 1800 and 2100 it is most practical to remember the anchor days for the 19th, 20th, 21st and 22nd century: For dates outside of this time frame you can simply rely on the 4...
To determine the doomsday of the year in question, you have to follow a series of 6 simple calculations. Before you start, don't forget to memorize the weekday numbers (see step 1) and century anchor days (see step 2). To illustrate the calculations, an example is given for each - let's say we want to find out which day of the week February 11, 197...
Now it is only a small step to the final result. You know the doomsday of the year (in 1978, it was Tuesday), and you know which dates of the year are doomsdays. Now you can simply use the doomsday closest to the date in question to find out which weekday it falls on. In the example date of February 11, 1978, the closest doomsday is the last day of...
How to Mentally Calculate the Day of the Week for Any Date. The so-called doomsday algorithm uses clever mental arithmetic and mnemonic tricks to enable a quick determination.
Feb 22, 1994 · The Doomsday Algorithm was "latest link in the braid" for the week of April 6-12, 1999. "This page will teach you a simple algorithm to calculate mentally the day of the week corresponding to any given date. Give it a try, it's quite rewarding! The page features clear instructions, examples, and mnemonic tricks."
The Doomsday rule is a method devised by John Conway for computing the day of the week of any given date. The method is based on first computing Doomsday , which is the day of the week of the last day of February.
Conway’s Doomsday Rule The rule referred to is a calculational procedure or mnemonic for determining the day of the week from the date. For simplicity we restrict ourselves to the 20th and 21st centuries, although one can also apply the method to earlier times. We associate each day of the week with one of the numbers 0 through 6, as follows ...
