Off the top of my head, I cannot think of any other mathematical terms that have their own special holiday or public commemoration than π (pi). The number π is special because it has two commemorative days.
The number π is usually the first irrational number we learn in school. It may even be the first Greek letter we learn, as well. Due to the fact that π is an irrational number, it’s representation as a decimal goes on for infinity and does not form a permanent repeating pattern that we know of.
That digital representation’s first few digits are 3.14159… the ellipsis is usually added to the end of however far that pi has been calculated. The number is often simplified to 3.14 for quick calculation purposes. It is this simple form that looks like March 14th by the American way of writing dates in number form–month then day–3/14 or March 14th.
Although π is an irrational number mathematicians sometimes approximate it with rational numbers including the convenient fraction 22÷7 or 22/7. When we use the European form of writing dates in numbers–day then month–we get 22/7 or the twenty-second of July. Because 22/7 is an approximation, some folks say that 22÷7 is “casual pi”. Therefore, today is Casual Pi Day.
When I punch the number 22 into my old Sharp calculator and divide it by 7, the read-out says, “3.1428571”, this result already deviates from the standard digital form following 3.14.
How can we celebrate Casual Pi Day? You could eat some special pi day pie, doodle circles or draw sketches containing several circular forms onto paper, or watch the movie “Life of Pi”. If you have a more serious personality, you might want to celebrate by investigating the number π then see to how many places you can calculate it.
I hope you have a Happy Casual Pi Day. Enjoy learning something today to make yourself more well-rounded.