Is your birthday special?

Only quants can have fun with dates that doesn’t involve snogging.

Financial expert/blogger David Markel defines a special birthday as one where you can create a simple math equation from the date.

For example, David was born Dec. 5, 1960. That, of course, is 12/5/60, and 12 x 5 = 60. There are also special days for:

  • Addition (1/1/02 is an example)
  • Subtraction – (12/5/07)
  • Division – (8/1/08)

Fun idea, right? Not sure how you count European dating, where the date precedes the month, i.e., 12/5/07 would be 5/12/07.

Brushing that aside, here’s the big question: Over a 400-year arc (has to be 400 to properly handle the leap-year cycle), how many birthdays are special?

The answer, and the methodology, are here.


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