# Happy Pi Day! (Note: This Is NOT Pi Approximation Day!)

**Posted:**March 14, 2013

**Filed under:**Holiday Leave a comment

**Other Pi related days you can celebrate (Pi Approximations)**:

- July 22: When 22 is divided by 7, it equals 3.14.
- March 4: When 14% of the 3rd month has elapsed.
- April 5: When 3.14 months of the year have elapsed.
- April 26: The Earth has traveled two radians of its orbit on this day (April 25 in leap years). This is celebrated exactly on the 41st second of the 23rd minute of the 4th hour on April 26 or the 116th day. (In leap years, it is celebrated exactly on the 3rd second of the 2nd minute of the 12th hour on April 25 or the 116th day.)
**If you keep track of this, I will bake you a pie.** - November 10: The 314th day of the year (November 9 in leap years).
- December 21, 1:13 p.m.: The 355th day of the year (December 20 in leap years), celebrated at 1:13 for the Chinese approximation 355/113.

**What is Pi?**

Pi (π) is the mathematical constant that has been known for almost 4000 years. Its value is the ratio of any circle’s circumference to its diameter in Euclidean space or the ratio of a circle’s area to the square of its radius. The value of pi is approximately equal to 3.14159265, but it is an irrational number and its decimal representation never ends or repeats.

The lower case Greek letter π is used because it is the first letter of the Greek work περίμετρος (perimeter), which probably refers to its use in the formula perimeter divided by diameter equals the constant for all circles. The concept of π has become the most common ground between mathematicians and non-mathematicians.

I love pie.