Pi Approximation Day / Pi-benaderingsdag 2026
2026-07-22
Pi Approximation Day is observed every year on July 22 all around the world.
The fraction 22/7 is an approximate value of Pi, and there behind lays a specific reason why this day is observed on July 22. This day is celebrated on July 22 every year because the value of Pi is denoted by the fraction 22/7. Here, in the fraction 22/7 which denoted Pi, the numerator 22 symbolizes the date (22nd day of the month) and numerator 7 indicates the month (July). Approximations for the mathematical constant pi (π) in the history of mathematics reached an accuracy within 0.04% of the true value before the beginning of the Common Era. In Chinese mathematics, this was improved to approximations correct to what corresponds to about seven decimal digits by the 5th century. Further progress was not made until the 14th century, when Madhava of Sangamagrama developed approximations correct to eleven and then thirteen digits. Jamshīd al-Kāshī achieved sixteen digits next. Early modern mathematicians reached an accuracy of 35 digits by the beginning of the 17th century (Ludolph van Ceulen), and 126 digits by the 19th century (Jurij Vega), surpassing the accuracy required for any conceivable application outside of pure mathematics. The record of manual approximation of π is held by William Shanks, who calculated 527 decimals correctly in 1853. Since the middle of the 20th century, the approximation of π has been the task of electronic digital computers (for a comprehensive account, see Chronology of computation of π). On June 28, 2024, the current record was established by the StorageReview Lab team with Alexander Yee’s y-cruncher with 202 trillion (2.02×1014) digits.
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Pi Approximation Day History, Meaning, Significance, other Celebration ideas
