Rather belatedly, I just discovered PI Day.
Because it was Mother's Day last Sunday it rather obscured the fact that in the USA, Congress has ruled that 14th March is PI Day - because PI to 3 significant figures is 3.14, as in 3/14 (MM/DD format).
This means we in the UK missed out on seeing a clever Google logo with circles and stuff (see http://www.ginside.com/2010/3952/google-pi-day-2010/), and got a warm and fuzzy Mother's Day
Before we rush to have a PI Day of our own in the UK/EU, using the DD/MM notation, hold fast - that means that PI Day UK would have to be on 31st April (31/4), which might cause a problem ("30 days hath September, April .....")
But that can be solved : we can have a "PI Approximation Day" on 22nd July instead (remember before they invented calculators when every school maths question used 22/7?).
For the nerds, the US often have an extra special event set for "Pi minute" (or should that be second?) at 1:59 (as in 3.14159).
Put it in your diaries, but March 14th, 2015, 9:26:53 is going to be extra special as it will represent PI up to the 9th decimal place (3.141592653) - yes I know there's a suppressed leading zero before the 9, but get a life, its meant to be a bit of harmless