# Pi Day: Circle Your Calendar -- Once-in-a-Century Day Coming This Weekend

A Pi Day like this won't come around for another century.

— -- Circle around, math fans. There's a once-in-a-century Pi Day coming this weekend.

The day that celebrates the mathematical constant pi is Saturday. And because it's 2015, this particular sequence of numbers in the calendar that matches pi -- 3/14/15 -- won't come around for another century.

While the mathematical constant, which represents the ratio of circumference of a circle divided by its diameter, is often abbreviated as 3.14 for convenience, pi actually has an infinite number of digits beyond the decimal point, starting with 3.141592653.

So, expect a good deal of celebration at 9:26 a.m. at 53 seconds -- with the pastry pie, for obvious phonetic and geometrical reasons.

In fact, there will be a point between 9:26 a.m. 53 seconds and 54 seconds that the clock matches the number pi down to an infinite number of digits.

And as befitting its reputation as an elite institution of math, science and engineering, the Massachusetts Institute of Technology has announced that it will send out its acceptance letters for this year's incoming class on Pi Day, precisely at 9:26 a.m.

That should round out the day -- at least for those accepted.