Pi Approximation Day

July 22 is 22/7, the fraction that has stood in for pi for two thousand years.

Pi Approximation Day on July 22 marks the date 22/7, the fraction most commonly used as an approximation of pi in contexts where the full decimal is unnecessary. The fraction 22/7 equals approximately 3.14286, accurate to pi (3.14159...) to about 0.04 percent. It was used by Archimedes in the 3rd ce