Geoff Canyon's Appeal to Authority

## Look Like a Genius

Calculating the day of the week for historical date is impressive, but it isn’t as hard as it seems. Several methods have been shown to work and be performable by average humans. This is an improvement to one of the simplest methods.

## The Doomsday Rule

Paraphrased from wikipedia:

The Doomsday rule or Doomsday algorithm is a relatively simple way to calculate the day of the week of a given date. It was devised by John Conway, drawing inspiration from Lewis Carroll’s work on a perpetual calendar algorithm. The algorithm takes advantage of the fact that several easy-to-remember dates fall on the same day each year; for example, 4/4, 6/6, 8/8, 10/10, 12/12, and the last day of February are all the same day of the week.

Conway’s original algorithm required dividing by 12 and 4, and remembering several intermediate values. It’s achievable, but not…

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