Tires

Although your question is about consumer tires, the week and year of manufacture is the same no matter what kind of tire is at issue. In your case, the 312 indicates that the tire was built during the 31st week of 1992. In early 2000, the date code system was changed to a 4 digit code (MMYY). In other words, 1203 would mean that the tire was produced in the 12th week of 2003. Tires (particularly commercial truck tires with multiple retreads) were in service for so long, it was often not possible to determine if they were 1 year old or 11 years old with the old 3 digit system. The new system designates the decade as well as the final digit of the year.