A tire's identification code is stamped on its sidewall and begins with the letters DOT. The last four digits of the tire identification code on a tire indicate the year and week of its manufacture.
The last four digits of this code indicate the week of manufacture in the first two digits and the year in the second two. For example, a tire manufactured in the seventh week of 2012 would have a TIN with the last four digits 0712. The Department of Transportation has mandated this information be included in the identification code on all tires sold in the United States since 2000.
Tires manufactured before the year 2000 used the last three numbers in the identification code to identify the tire's manufacture date, with the first two of these indicating week and the last indicating year. Therefore, there is no way to differentiate a pre-2000 tire manufactured in 1998 from one manufactured in 1988 from the code alone.
Determining the age of a tire is important when purchasing a vehicle with used tires, as tires age and may become unsafe even if they are not seriously worn from driving. Many car manufacturers recommend replacing tires older than five to seven years old, even if the tires still have tread remaining. Manufacture dates also help determine if a tire was subject to a recall.