Good news, math geeks. March 14 marks this year’s official recognition of National Pi Day, a holiday honoring the existence of the mathematical constant.

Pi Day is celebrated every year on March 14 because the first three digits of pi are three, one and four, much as the date is represented numerically as 3/14. The constant is also represented by the Greek letter π.

In 2009, the United States House of Representatives officially recognized March 14 as National Pi Day. However, the holiday was invented well before that declaration was made.

The earliest known Pi Day celebration occurred in 1988, when physicist Larry Shaw organized a party at the San Francisco Exploratorium. Participants celebrated the mathematical constant by walking around one of the building’s circular areas and by eating actual pies, the Fresno Bee reported.

In fact, pies are frequently included in Pi Day activities. Fans of mathematics often hold pie-eating or pie-throwing contests on March 14, CNN reported. The celebration has also produced various T-shirts and discussions about the significance of pi.

But pi’s influence extends far beyond a few tongue-in-cheek parties. The mathematical constant is essential to performing the feats of engineering that make modern construction possible, such as the use of arches.

Essentially, pi is the ratio of any circle’s circumference to its diameter. As an irrational number, π is a never-ending decimal; scientists are constantly attempting to determine additional digits of pi. As of today, pi has been calculated up to trillions of numbers beyond its decimal point, USA Today notes. For simplicity’s sake, pi is most often rounded off at 3.14, or 3.14159.

As if all of that weren’t enough for math geeks, Pi Day happens to fall on Albert Einstein’s birthday. Coincidence? We think not.