All tires sold since the late 1960’s to 1999 have a DOT number on the sidewall which ends in a three digit code (two digit week, one digit year) meaning that a tire with a DOT number ending in 253 would have been manufactured the 25th week of a year ending in 3. All tires made since the year 2000 have a four-digit code so that a tire with 4004 would have been made in the 40th week of 2004.