We love and celebrate Pi Day here at the Engineering Library on or around the traditional day of March 14th (3/14), but did you know that there another Pi Day? Pi can be expressed with the fraction 22/7, so if you’re partial to pastry, you can celebrate Pi Day on July 22nd. You can also call it pi approximation day, if you want to be more formal.

Here’s some fun Pi facts to get you started with your celebrations:

- If you don’t want to use the word “pi” or are looking for alternatives, you can use “Archimedes’ constant,” “the circular constant” or “Ludolph’s number.”
- Mathematician William Jones first proposed using the Greek letter as shorthand for the constant in 1706. Before its adoption, pi was referred to by a Latin phrase which roughly translates to “the quantity which, when the diameter is multiplied by it, yields the circumference.”
- The world record for memorization of decimals of pi is 70,000 and is held by Rajveer Meena. Meena established this record in 2015 and wore a blindfold for the 10 hours it took him to complete this feat. If you want to try your hand at beating the record, you can use techniques like memorizing smaller groups or spatial visualization techniques.
- You don’t need 70,000 digits of pi to make accurate calculations. The Jet Propulsion Laboratory uses the first 15 digits after the decimal (3.141592653589793) for interplanetary navigation calculations.
- The first known algorithm for calculating pi used polygons. Archimedes calculated pi by calculating the perimeters of inscribed and circumscribed polygons. He doubled the number of sides of the polygons, finally reaching a 96-sided polygon and found that pi was between 223/71 and 22/7 (does that number look familiar to you?).