Saturday’s ‘Pi Day’ a once-a-century event

Saturday will be a very special day for mathematicians with an event that only occurs once a century.

March 14 has become a popular informal holiday, Pi Day, to celebrate the mathematical constant ’π’ or ’Pi.’ It’s the Greek letter given to denote the ratio of a circle’s circumference to its diameter. Though having decimal places that are estimated to be infinite, it’s often shortened as 3.14.

So on the date 3-14 every year, many have celebrated Pi Day — often by eating actual pie. The popular day even has its own website, piday.org.

But Saturday will be the only time for the next 100 years that the year will also match the next two numbers in Pi: 3-14-15. Though some world cultures put the year or day first while writing dates, the American practice of putting months first means it will be the only time this century the date matches up with the first five digits of Pi.

And people can take it a step further if they want, matching up the next five digits of Pi with the time: 9:26 and 53 seconds.

So on Saturday, 3-14-15, at 9:26:53 a.m. or p.m., celebrate. And have a slice of pie.

Though less rare, Friday is also the 13th, a common superstition that the day and date are bad luck. It even lent its name to a popular horror movie. But in February, the 13th fell on Friday as well, making this an uncommon year with two consecutive “Friday the 13th.”

The last time a year had the 13th fall on a Friday for two consecutive months was 2009, and it was also February and March.

It’s next predicted to happen again in 2026 — again with February and March. February’s shortened month of 28 (sometimes 29) days means it’s easier for the dates in the second and third month to align.

For those who prefer history to mathematics, Sunday will be the Ides of March, a Roman holiday commonly credited as the day that Julius Caesar was assassinated.