An e-pi-c day is coming! On 3.14.15 at 9:26:53; the date/time will correspond to the first 10 digits of the mathematical constant pi (3.141592653). This happens only once per century — a truly once-in-a-lifetime event for most people.

The mathematical constant, which is the ratio of a circle’s circumference to its diameter, can be used to find the area or circumference of circles. PiDay.org explains that “pi has been calculated to over one trillion digits beyond its decimal point. As an irrational and transcendental number, it will continue infinitely without repetition or pattern. While only a handful of digits are needed for typical calculations, Pi’s infinite nature makes it a fun challenge to memorize, and to computationally calculate more and more digits.”

• Read more: 9 Great Reads about Pi, The World’s Favorite Mathematical Constant

In 2009, the United States House of Representatives declared March 14 (3.14) to be National Pi Day. They passed resolution HR 224 to celebrate the importance of math, science and education in our lives, while sparking interest in learning and reminding the public of the importance of strong STEM (science, technology, engineering and math) education as a vehicle to inspire ongoing innovation in the upcoming generation. Today, Pi Day is celebrated throughout the world, even in countries that don’t list the month and day in that order. Traditionally, official Pi Day celebrations begin at 1:59 (ideally at 26 seconds), but in 2015, the year will be incorporated, and participants will be counting down to exactly 9:26:53.

• Read More: Are you a Tau-ist? Pi Day is Under Attack

People celebrate Pi Day around the world with pie-eating, pie-throwing and even pi-recitation contests, where participants recite digits of this irrational number from memory.

• On the Web, the piZone has been promoting pi day activities with a variety of products and platforms that inform and inspire STEAM education, including a series of piZoneSocial videos.
• March 14 also happens to be Albert Einstein’s birthday, and the day takes on special significance in his hometown of Princeton, NJ, where festivities will begin this year at 7am and continue until 9:26:53 p.m.
• At the San Francisco Exploratorium, where the earliest known large-scale celebration of Pi Day was organized in 1988, the museum will “serve up pi-themed activities, rituals, antics and plenty of pie,” as well as an “annual march to the Pi Shrine” — a metal disk that is engraved with the first 100 digits of pi.
• On a more serious note, MIT has announced that “admissions decisions for the Class of 2019 will be posted online on Saturday, March 14, 2015 beginning at 9:26 AM” (which some believe to be a much better choice than Friday the 13^th).
• While in Fort Meade, MD, the NSA’s National Cryptologic Museum will offer a variety of family-friendly activities, including crafts and the story of “Sir Cumference and the Dragon of Pi.” Plus, visitors can figure out the diameter of their heads using pi.
• And in New York City, The National Museum of Mathematics (MoMath) will gather hundreds of math enthusiasts in Madison Square Park to create a “stunning illuminated demonstration of the meaning of Pi” by surrounding Madison Square Park’s north fountain entirely with glowing light sticks — the distance around the shimmering circle can be compared to the distance across it, showing the true meaning of pi.
• Even the American Pie Council joins in the fun, offering a free Pi Day Activity Packet and “encouraging pie lovers everywhere to enjoy some pie in honor of Pi Day.”

So, however, you may choose to celebrate, remember to join in the big 3.14.15 countdown to 9:26:53!