(X-Y) + (Y-1900) = ?

X = Current Year ; Y = the Year you're born

With (X-Y) we get our age, with (Y-1900) we get the last 2 digits, so you'll get 111

example: in my case, I born in 1978, I have 33 years so

X=2011 ; Y=1978

(2011 - 1978) + (1978 - 1900) = 111

But if we take out the () from the formula, we get; X - Y + Y - 1900 = X - 1900

Once again, if X=2011 we get 2011-1900 = 111 .... there you get the 'Magical' 111