Whether or not you're a math geek, you know pi, or at least the beginning of it: 3.14. The infinite, irrational constant, without which you couldn't find the area of a circle, gets its day each year on March 14 (3/14).
But this year is special.
If you stretch out pi to its third and fourth decimal places, you get 3.1415, making March 14, 2015 (3/14/15) the ultimate tribute. And unless you're 117-year-old Misao Okawa, the world's oldest person, it's a once-in-a-lifetime event. It won't happen again until the year 2115.
Whether you are celebrating with a math marathon or a pie-eating marathon (or a combination in which you use pi to figure out how much pie you just ate), if you really want to do it up this year, plan something for 9:26 and 53 seconds, stretching your commemoration all the way out to 10 digits.
This story originally appeared on CBSNews.com.