This Saturday is not only Pi Day (3.14), but it’s the Pi Day of the Century (3.14.15).

Pi, or π, is the ratio of the circumference of a circle to its diameter. It’s usually shortened to 3.14, which is why March 14 is celebrated every year as Pi Day, but it’s an irrational number that continues infinitely without a pattern, like so: 3.14159265358979323846264338327950288419716939937510582…