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## Another Calendar Feat Approach

Published on Thursday, April 30, 2009 in , , , , , , ,

One of the more popular features of this site is the Day of the Week For Any Date tutorial. While this is my favorite method, I'm not averse to other effective approaches. For example, there's my specially-made calendar that helps make determining the day of the week easy without even opening it, as well as the Doomsday method for the current year I taught back in mid-January.

Here's another approach, with a detailed explanation of the whys and wherefores of each part of the method, courtesy of math buff James Grime. Grey Matters readers will likely enjoy perusing his YouTube channel.

If you're already in the process of learning from my tutorial, don't learn the method below, as different key numbers are used for the days. However, if you've found the other methods troublesome, perhaps this approach will work for you:

There are a few details in the video description that should be noted:
If you give me your date of birth I can tell you the day of the week on which you were born.

Some information:
This was a presentation for a job in Cryptography, hence the punchline about Enigma. I got the job.

Not mentioned in the video, if it's January or February of a leap year we need to subtract 1 (since we are counting leap days).

If I'm counting from 1899 why do I add 41 instead of 42? Because the date must be at least 1 - that automatically pushes us into 1900 and we count the years from there.

The sound is rubbish because Vista is giving me problems.
I happened to be thinking about the calendar feat today because a recent contestant on the British game show Countdown (if you're not familiar with the show, see James Martin's legendary appearance on that show here) performed that same feat, and several readers from a Countdown forum (Warning: Foul language at that link) came to my site to learn how the feat was done.

If this isn't enough incentive to learn the calendar feat, think about the fact that 6-year-old Sean (below) can master the feat! When he's working out the final date, he verbalizes his thought process, and he seems to be using a version of the Doomsday method I mentioned at the beginning of this post. The fact that he can determine the day of the week for any date in 2009 is especially interesting when contrasted with his mom, who apparently has trouble just starting and stopping the video camera.