A holiday associated with a math concept may not seem that exciting, especially for those not fond of the subject. However, America's Pi (“π”) Day – observed annually on March 14 (3/14) to honor the ratio of the circumference of a circle to its diameter, widely recognized as 3.14 – is an exception. That's because the celebrations don't just include fun math activities, but also a slice, or two, of yummy pie!

The tradition of honoring the geometrical constant, whose precise value remains elusive even after being calculated to over thirteen trillion digits beyond its decimal point, began at San Francisco’s Exploratorium Museum. On March 14, 1988, at 1:59 PM PST, the museum's then-technical curator, the late Larry Shaw, convinced colleagues to celebrate the day – which also happens to be Albert Einstein's birthday – by parading around one of the museum’s circular spaces and consuming fruit pies. The group had such a good time that museum officials decided to make Pi Day an annual event where visitors are treated to special pi-related activities, including a parade to a special "Pi shrine," and, of course, some delicious pie. Schools, libraries, and universities, around the country, soon began organizing similar activities and in 2009, US lawmakers made the celebration official by declaring March 14 as Pi Day!

Today, Pi Day is celebrated in many creative ways. To encourage more girls to seek out careers in science, technology, engineering, and mathematics (STEM), female television meteorologists wear what is referred to as "The Dress" every March 14. The outfit became famous after a viewer posted an image of hundreds of forecasters coincidentally wearing the same dress in various colors on social media in 2016. Those who do not own "The Dress" will show their solidarity for the vital message by wearing blue.

The town of Princeton, New Jersey, where Einstein resided from 1935 until his death in 1955, combines Pi-Day and the scientist's birthday with "an irrational number of events" which include pie-eating, pi-recitation, and Einstein lookalike contests.

For the past six years, NASA's Jet Propulsion Laboratory has observed Pi Day with an online "Pi in the Sky Challenge." Designed for students in grades 6-12, it comprises four real-world problems faced by NASA scientists and engineers. This year, kids can help the experts figure out how to weather a Mars dust storm, measure a shrinking storm on Jupiter, estimate the water content of a rain cloud on Earth, and blast ice samples with lasers!

High school seniors aspiring to attend the Massachusetts Institute of Technology (MIT) eagerly await Pi Day every year to find out if they have been accepted to the elite university. However, the e-mail notifications are not sent out at 3:14 PM EST as would be expected but at 6:28 PM EST. Referred to as Tau, the constant, derived by multiplying 3.14 by 2, is believed to be much more reliable than pi by some experts and even has its own special celebration on June 28. Since 2017, MIT, and many other colleges across the country, have also been using Pi Day as a fundraiser to raise much-needed money for students, faculty, and programs.

Many retailers also get into the spirit with limited-time deals on pies, pizzas, and other goodies. This year diners at Marie Callender's restaurants will receive a free piece of pie for every adult entree bought, while those at California Pizza Kitchen will get the same at a discounted price of $3.14. Those craving a pizza will be able to order a large, three-topping, pizza at Pizza Hut for just $7.99, or take advantage of Papa John's generous buy-one-get-one-free offer.

Though the pie eating traditions are relatively recent trends, pi has been around for thousands of years. The Babylonians were the first to use it 4,000 years ago to calculate the area of a circle by taking three times the square of its radius – giving pi a value of 3. The ancient Egyptians came closer to the real number with 3.165 in 1650 BC. Archimedes of Syracuse (287-212 BC) was the first to calculate pi mathematically. However, the Greek scholar was well aware that his number, which ranged between 3 1/7 and 3 10/71, was just an approximation. Given that the pi estimates were calculated without any help from computers, their proximity to the mathematical constant's real value is truly astounding.

Resources: Wikipedia.org, Jpl.Nasa.gov, exploratorium.edu.