Pi Approximation Day
Pi Approximation Day is held on July 22. This event in the third decade of the month July is annual. 
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Pi, or π, is the ratio of a circle's circumference to its diameter. Because it is irrational, it can't be written as a fraction. Instead, it is an infinitely long, nonrepeating number.
The record for the most digits of pi memorized belongs to Rajveer Meena of Vellore, India, who recited 70,000 decimal places of pi on March 21, 2015, according to Guinness World Records.
The Babylonians thought the fraction 3 1/8 was good enough in 2000 B.C., while the ancient Chinese and the writers of the Old Testament (Kings 7:23) seemed perfectly happy to use the integer 3. But by 1665, Sir Isaac Newton had calculated pi to 16 decimal places. By 1719, French mathematician Thomas Fantet de Lagny had calculated 127 decimal places. And late last year, Peter Trueb, a scientist at the Swiss company Dectris Ltd., used a multithreaded computer program to calculate 22,459,157,718,361 digits of pi over the course of 105 days.
Similar holidays and events, festivals and interesting facts
International Day of Junk Food on July 21
Hammock Day on July 22 (Nothing sounds quite as relaxing);
Ratcatcher's Day on July 22 (or Rat Catcher's Day is celebrated on 26 June or 22 July, commemorating the myth of the Pied Piper of Hamelin.);
One Piece Day on July 22
Schwörwoche and Fischerstechen in Ulm on July 22 (A celebration of tradition and cohesion);
Drive-Thru Day on July 24 (Restaurants, coffee shops, liquor stores, pharmacies and many more services utilize drive-thrus for quick service);
Lumberjack Day on July 25
Thread the Needle Day on July 25
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