CN. Name That Date
John. H. Conway, one of the young men pictured above, tells us about his fabulous and simple method for rapidly calculating the day of the week.
With just a little practice, you too can Impress your friends (or drive them away) with this stupendous ability!
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strauss said,
May 27, 2007 at 10:49 am
In the epsiode, we talked about how to find the day of the week of any date in the XXth Century, a “Wednesday Century”. The current century is a “Tuesday Century” and the method works the same way, counting from Tuesday.
But we didn’t mention what kind all the other centuries are:
In the Gregorian Calendar, the centuries roll around thusly:
1200 1600 2000 2400 etc are Tuesday centuries.
1300 1700 2100 2500 etc are Sunday centuries.
1400 1800 2200 2600 etc are Friday centuries.
1500 1900 2300 2700 etc are Wednesday centuries.
However, today is Sunday May 14, 2007, in the Julian Calendar, and the Julian centuries work thusly:
000 700 1400 etc are Sunday centuries
100 800 1500 etc are Saturday centuries
200 900 1600 etc are Friday centuries
300 1000 1700 etc are Thursday centuries
400 1100 1800 etc are Wednesday centuries
500 1200 1900 etc are Tuesday Centuries
600 1300 2000 etc are Monday centuries.
In many Catholic countries, the day after Thursday October 4, 1582, in the Julian calendar, was Friday October 15, 1582, in the Gregorian. This change came later in other places; the British Empire switched nearly two centuries later, and Russia only in 1918. Wikipedia has a fascinating discussion of this history.
Curiously, then, all would agree that the English defeated the Spanish Armada on a Monday but was the date August 8, 1588 (as according to the Spanish) or July 29, 1588 (as according to the English)?