Pi Day is celebrated annually on March, 14 (3/14 in the month/day date format). Pi ( π) is that famous mathematical constant with an infinity of decimal places, and represents the ratio of a circle’s circumference to its diameter. This ratio is the same for all circles. Its first significant digits are 3.14.

Pi was also known as “that funny circumference-over-the-diameter number that goes on forever and ever and ever, and I’ll stop calculating it as soon as I find the pattern.” everydaysaholiday

Pi Day’s first official celebration was held in 1988 at the San Francisco Exploratorium. Pi Day has been observed in many ways, including marching around circular spaces,  eating fruit pies, throwing pies and discussing the significance of the number π.

In 2009 the U.S. House of Representatives recognized March 14, 2009 as National Pi Day. There is also an European equivalent, Pi Approximation Day, celebrated on July 22 (22/7).

On March 14, 2015 is the first time and the only in a century that the date is 3/14/15, which describes the first five digits of pi, 3.1415. At 9.26:53 am  the date and time described pi to 10 digits. Some people say the only real Pi Day was March 14, 1592. (3.14 1592), even that was only accurate to 7 digits.

How to have fun on Pi Day

1. You can try to beat the record of memorizing Pi’s digits.

source: spikedmath

The Guinness-recognized number of remembered digits of π is 67,890 digits, held by Lu Chao, a 24-year-old graduate student from China. Mats Bergsten of Sweden holds the world record for memorizing Pi while juggling, reciting 9,778 digits in 1hr 20min.

2. If you find it hard to memorize, maybe you should try some choco-pi to boost your memory.

source:chocopi

3. If it doesn’t help, you can try an apple pie.

4. Still not working? Maybe you should relax and bake a pie.

Get the recipe from:  seriouseats

5. If you don’t succeed, don’t be sad, you still can calculate the volume of a pizza.

source: boingboing

6. Or you can still make a nerdy, but cute love declaration.

I will love you until Pi runs out of decimal places.

source: someecards

7. Maybe you’ll take a moment to meditate on Pi Day mystic sense.

source: freakingnews

8. Somehow you’ll realize how limited knowledge can be and let your imagination to fly.

“Knowledge is limited. Imagination encircles the world.” — Albert Einstein

Believe it or not Albert Einstein was born on Pi Day, 14 March 1879.