I recently came back from a few weeks holiday to find a rim with an old tire on it had completely deflated. The tire was needing replacement anyway so I took it to a tire shop to get a new tire put on. When he saw the tire, the fitter said "Wow. That's old." and pointed to a code that said 05 on the sidewall. He stated that it was manufactured in 2005 and so (given that it's now 2016) was a very old tire.
Do most/all tyre manufacturers put these dates on the sidewall? It would be very informative when doing a car (or tire) purchase to be able to determine the age of the tires.