Menu| Instructions | Example: November 12, 2070 |
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Step 1: Determine the code for the century:
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Century = 2000's The code for 2000's is 6 Shortcut: Use -1 instead of 6 for 2000's to make the arithmetic easier. Total = 6 |
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Step 2: Determine the code for the year:
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Year = 70 68 is 2, so 69 is 3 and 70 is 4! Total = 10 (6 + 4) |
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Step 3: Determine month code:
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Month = November November = 2 Total = 12 (6 + 4 + 2) |
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Step 4: Determine date code:
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Date = 12 The code for date:12 is 5. Total = 17(6 + 4 + 2 + 5) Shortcut #1: Subtract 7, 14, 21 or 28, from the date to find code, dates less than 7 are already equal to the code. Example: Nov 12: 12 - 7 = 5. Example: Nov 26: 26 - 21 = 5 Shortcut #2: Simply add the date to the total. Example: Nov 12: Code=12, Total = 24 (6 + 4 + 2 + 12). |
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| Step 5: Determine day-of-week from total Divide the total from Step 3 by seven, the remainder giving the day-of-week:
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Total = 17 (Century=6, Year=4, Month=2, Date=5) 17 divided by 7 is: 2 remainder 3 3 = Wednesday Shortcut: Instead of dividing, just subtract 7, 14, 21, 28, or 35, etc. (multiples of 7) until you have a number 0 to 6. For example, 17 - 14 = 3. If the total was 30, then 30 - 28 = 2 = Tuesday. More Flashcards |
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| Step 6: Don't forget leap-year! Subtract 1 at any point in the process only if the year is a leap year, and the month is January or February! |
2070 is not a leap year. Shortcut #1: The year is a leap year if it is found in the table in step 1. (68 and 72 are leap years, but 70 is not) Shortcut #2: A year is a leap year if it is evenly divisible by 4. Shortcut #3: As a last step, you can simply take the day before (if the year is a leap year, and the month is Jan. or Feb.) Click here for the rare exceptions to the above shortcuts. |
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Click here for flashcards for 1800 to 2199.
Tips and Tricks
• Some may find it easier to combine the century and year code first, then combine the month and date code, and then add the 2 numbers together for a final total, and proceed to step 5 from there.
• Click here for a printable one-page quick reference.
• Please let us know your success stories if you master this system!
Links
• Calendar Memory Records
• Doomsday Algorithm - Gaudy yet informative site showing a different approach to the human calendar, originally created by mathematician-great John Horton Conway