Yesterday was square root day, and we imagine that most of you celebrated it in the customary fashion by eating square vegetables. It was square root day because the date was 03/03/09 and 3 times 3 is 9. The last square root day was on the 2nd of February 2004, and the next one will be on the 4th of April 2016, so they're relatively rare occurrences. Far more common are Plus's own invention, addition days. The coming Friday is one of them, because the date will be 06/03/09 and 6+3=9. Of course there could also be subtraction days, or maybe exponential days. In fact, with a bit of numerical skill, you can probably turn every day into a maths holiday.

A far more serious affair is World Maths Day, which is in fact today. It's celebrated on the first Wednesday in March and involves student and student groups from around the world competing to solve 182,445,169 mental arithmetic challenges in 48 hours. The winners receive medals and certificates, but of course it's the glory of winning that counts, and last year this was bestowed on teams from Malaysia and the UK, as well as individual students from Australia and the UK. It's too late to register for this year's event, but why not start practicing for next year?

Happy maths day!