If 30 is the new 20, it stands to reason that 50 is the new 40 - because math.

Plenty of celebs this year hit the big 5-0, which means they're only 15 years shy of that coveted senior citizen discount and the right to yell at kids to get off their lawns.

Some -- like Jon Stewart -- have gotten better with age, while others may or may not be drinking the blood of virgins to keep their immortal glow. (We're looking at you Demi Moore.)

Check out our list of the celebrities who turned 50 in 2012 -- and try not to feel old yourself when you see Ferris Bueller among them.