The other day in Astronomy, we talked about how time has been measured throughout history, and how even the Gregorian calendar we use today isn't 100% accurate.
Then our teacher told us about a little something called Julian date.
It's fairly simple: the current date is the amount of days since sometime in the 4Ks BC.
Or, to put it another way, it's stardate, like in Star Trek. Made all us nerds in the class rather giddy, to say the least.
Edit: if you're wondering, the current Julian date is approximately 2457264.056250.