You might have seen all the “Happy Pi Day!” messages going around the various social networks, and ordinarily I’d be very keen to do a fun little graphic to join in with the revelry. But the simple fact is I can’t get behind this particular mathematical festival because it simply doesn’t make sense to me.

**Today is not “Pi” day, regardless of how much I’d like it to be.**

In fact today is just the 14th of March, 2014: Written correctly the date today is 2014/03/14 and, as far as I know, there is no mathematical significance to the number 20140314. Now some of you might be thinking that I’ve written that date backwards, but I can assure you I have not. You can argue backwards and forwards the merits of the American date system (MM/DD/YYYY) versus the British date system (DD/MM/YYYY) but ultimately both are incorrect.

**There is only one correct way to write the date**

…and that is year, month, day. If you want to write the time too, then you can follow the date with the time: YYYY/MM/DD hh:mm.ss

And why is this the correct way to write the date? Because it flows from largest units to smallest units. The year is larger than the month, the month is larger than the day, the day is larger than the hours, etc. A date is just a number, and this is how we write numbers: The larger units come first, and we proceed to the smaller numbers. So it’s mathematically correct.

Not convinced? Try this then. Try sorting a list of dates in the American system, here are a few as an example:

12/01/2013

03/14/2014

03/14/2013

01/12/2013

Sorting these dates means first sorting by the year – at the end of each date, then by the month – at the start of each date, and then by the day – in the middle of each date. Not simple. Here are the same dates in the correct format:

2013/12/01

2014/03/14

2013/03/14

2013/01/12

Sorting is now simple: The year is first, then the month, then the day. In fact you can sort this “alphabetically” in a computer (computers treat 0-9 the same way that they treat a-z) and it will still come out right.

**It will never be Pi day :(**

The sad fact is under the British system and under the correct system outlined above, it will never be Pi day in our lifetime. The closest thing to a Pi day will be 3141/5/9 under the “correct” date system or 3/1/4159 under the British date system, but even these are not entirely satisfactory Pi dates since they involve dropping the leading zeros off the day and month.

Not to mention that 3.14… doesn’t really define pi. It’s just pi in base 10, which is an arbitrary choice of base.

pi is more than its base 10 representation. That’s why I feel “pi day” goes against the spirit of mathematics.

Very true, maybe we should be celebrating 11th of March (in America – 3rd of November in the UK) for base 8. Or, and this has a charming ring to it, switch to duodecimal and you get 18th of March (which of course only works on the USA date system). Base 12 just makes sense when our calendar has 12 months!

Besides all of this tau is a considerably more useful and understandable constant anyway. After writing this article I found out there is a Tau day which is starting to gain traction: http://tauday.com/