Investigating National Pi Day

American Express is running ads for Small Business Saturday (November 27). It’s a good idea, but I was taken aback by one of their radio spots, which says:

There’s a day for everything — Thesaurus Day, Groundhog Day, National Pi Day…

That last one caught my ear. I’ve celebrated Pi Day for years, but National Pi Day? At first, I was sure the copywriters for American Express had screwed the pooch on this one. Pi Day cannot be a national holiday, because π is a universal constant. And the United States is not the only country that writes dates in the mm/dd format — so do Canada, Greece, Kenya, China, and the Phillipines, among others.

I did a little investigating. Sure enough, there is a National Pi Day. On March 12, 2009, the U.S. House of Representatives passed HRES 224, a non‑binding resolution that declares:

Whereas Pi can be approximated as 3.14, and thus March 14, 2009, is an appropriate day for “National Pi Day…”

The resolution continues:

The House of Representatives supports the designation of a “Pi Day” and its celebration around the world.

Doesn’t it seem a bit incongruous to declare a National Pi Day but then support its celebration around the world?

At least HRES 224 correctly states that π can be approximated as 3.14. This is in stark contrast to House Bill 246, passed by the Indiana State Legislature in 1897, which stated, among other things:

that the ratio of the diameter and circumference is as five-fourths to four

thereby implying that π = 16/5 = 3.2.

What a difference 113 years make, huh?

A geometry teacher hands a cylindrical metal container to a student and asks her to find the ratio of the circumference to the diameter. She thinks for a moment, then offers, “Um… pot pi?”