Why some people hate pi day

14 March is celebrated by some as the most exciting day in mathematics — when the date lines up in the numbers of the famous constant. But some people would rather it isn’t celebrated at all.

The day looks like 3.14 for those that write dates in the month then day format, but that is rarely used outside of the Americas. Many people instead opt to celebrate the potentially more interesting Pi approximation day, which takes place on 22 July or 22/7 — a way of working out an approximate value for Pi for use in rough calculations.

And still others would rather that Pi day wasn’t celebrated at all, and that the number shouldn’t be treated with such reverence. Instead, they say that we should use Tau — a number that serves much the same purpose and can be celebrated on 28 May, or 6/28 in America.

The complaints about the date are relatively obvious. Most places around the world use a different system to the US, where Pi Day was born.

By far the most popular date format is day/month/year, as is used in the UK as well as much of Asia, Australia, Africa and South America. It isn’t possible to write Pi day using that format, but it is easy to write Pi approximation day.

In China and many other countries in south-east Asia, dates are written year/month/day. It is possible to do Pi day in that format since the day (14) does follow the month (3), but the year comes first and throws that off slightly.

But the complaints about the competitor to Pi Day, Tau Day, are much more aggressive — and campaigners for the change have made a website and a full manifesto, laying out exactly why the world is wrong.

That manifesto, written by Tau fan Michael Hartl, is dedicated to the “true circle constant”, which he says should be referred to by the Greek letter Tau.