## This most perfect Pi Day: 3.14.15

Pi Day is celebrated on 14 march (3.14) around the world for obvious numeric reasons. But todayâ€™s Pi celebration is extra special because the date corresponds to the *first four digits* after the decimal point. That wonâ€™t happen again for another century.

The number â€œÏ€â€ [represented by the Greek letter since the mid-18th c.] is a mathematical constant. Itâ€™s the ratio of a circleâ€™s circumference to its diameter. Ï€ is an irrational number â€“ meaning it cannot be expressed exactly as a ratio of two integers. Its decimal representation goes on to infinity without repetition or pattern.

So in honor of this great Pi Day, while Ï€ is most often represented numerically as 3.14159, the above illustration shows what Ï€ looks like to its millionth decimal point. If you don’t believe me, download the PDF here.

Check out *Mashableâ€™s* list of 10 Pi facts to find out why this is the best Pi Day ever. And hereâ€™s *Timeâ€™s* list of some of the big celebrations. Enjoy!

*Whatâ€™s your Pi Day look like?*