I only found about this yesterday, via COSMOS online. Actually, it's Pi Day tomorrow in the US where it originated because, using American date nomenclature, March 14 (3/14) gives the first 3 digits of pi. But this year is special because the date is 3/14/15, which are the first 5 digits and it will be the only time in the whole century.
π, as everyone knows, is the ratio of the circumference of a perfect circle to its diameter, irrespective of the size of the circle. But it's a very nerdy number, because it turns up in the most unexpected places, like quantum mechanics and Euler's famous formula: eiπ + 1 = 0;
earning the sobriquet, 'God's own equation'. A simple derivation can be found here.
Pi is the best known so-called transcendental number and, of course, it has an infinite string of digits that appear to be truly random (refer COSMOS link above). COSMOS also explain that if you toss a coin 2n times, and n is large enough, then the probability of getting equal number of heads and tails is 1/√(nπ). Mathematics contains many hidden formulae like this that give unexpected relationships relevant to the real world.
Addendum: It should be pointed out that today is also Albert Einstein's birthday and this year is the centenary of his masterpiece, the General Theory of Relativity, not to be confused with the Special Theory, which he penned 10 years earlier in 1905.