7月22 Fun Holiday – Pi Approximation Day

July 22 is Pi Approximation Day. Also known as Casual Pi Day, the day is dedicated to the mathematical constant pi (π).

Pi denotes the relationship between a circle’s circumference and its diameter and is denoted by the fraction 22/7 which calculates approximately to 3.14. One of the most widely recognized mathematical constant, π, is an irrational number, the digits of which repeat in a random fashion and are never ending.

Depends on Date Format

People in countries that write their dates in the date/ month format celebrate Pi Approximation or Casual Pi Day on 22 July or 22/7. On the other hand, those who write their date in month/ date format celebrate Pi Day on March 14 (3/14 or 3-14) because the first three digits of the date correspond to the first three digits of pi - 3.14.

Move to Replace Pi

In recent years, some mathematicians and physicists have argued for the replacement of the π by tau and to celebrate Tau Day on June 28 instead of celebrating Pi Day or Pi Approximation Day.

How to Celebrate?

Here are some ways you can celebrate this irrational, but fun holiday:

• Celebrate the day with lots of pie – remember a pie is also a circle so not only are you learning something about math, but also having fun while eating it!
• Have a pi contest. Whoever knows the most digits in the number takes home a pie.

Did You Know...

...that the sequence 123456 does not occur in the first million digits of pi?

Pi Approximation Day Observances

Fun Holiday: Pi Approximation Day Observances
Year	Weekday	Date	Name
2025	火曜日	7月22日 (火)	Pi Approximation Day
2026	水曜日	7月22日 (水)	Pi Approximation Day
2027	木曜日	7月22日 (木)	Pi Approximation Day
2028	土曜日	7月22日 (土)	Pi Approximation Day
2029	日曜日	7月22日 (日)	Pi Approximation Day
2030	月曜日	7月22日 (月)	Pi Approximation Day
2031	火曜日	7月22日 (火)	Pi Approximation Day
2032	木曜日	7月22日 (木)	Pi Approximation Day
2033	金曜日	7月22日 (金)	Pi Approximation Day
2034	土曜日	7月22日 (土)	Pi Approximation Day

See all Fun Holidays