Date code (the last four digits of the DOT code)

How to read it

Under 49 CFR 574.5, the date code is the final group of the tire identification number. The first two digits are the week, counting 01 as the first full calendar week of the year, Sunday to Saturday; the last two are the year. The regulation’s own example is 0109: the week from Sunday, January 4 to Saturday, January 10, 2009. The final week of a year may include up to six days of the next year. The date may be moulded, or laser-etched within 24 hours of the tire leaving the mould. NHTSA’s example is 0308, the third week of 2008.

Also searched as: DOT date code, tire age, tire date code, tire manufacture date.

Three digits: tires made before 2000

Until July 2, 2000, the date code had three symbols: two for the week and one for the year. The Federal Register’s example, 218, is the 21st week of 1998, so a three-digit code gives only the last digit of the year. NHTSA moved to four digits in a 1999 final rule, after a petition from the Rubber Manufacturers Association, saying the change would allow easier identification of older tires. Makers could switch early, from the rule’s publication in July 1999.

Why the date may be on the other side

Since September 1, 2009, FMVSS 139 has required the full TIN, date code included, on the tire’s intended outboard sidewall; the other sidewall may carry a partial TIN without the date. NHTSA’s tire page says to look on both sides because the TIN may not be on both.

What NHTSA and tire makers say about age

NHTSA’s tire page says tires are more prone to failure as they age, and that some vehicle and tire manufacturers recommend replacing tires that are six to 10 years old, regardless of treadwear. It says the people most at risk own vehicles they don’t drive regularly, such as recreational vehicles, 15-passenger vans and collector cars, and that aging is a greater concern in the southern Sun Belt states. Nokian Tyres’ guide recommends using the same tires for a maximum of six years. The U.S. Tire Manufacturers Association puts it differently: its Tire Care and Safety Guide says tire service life is not determined by chronological age but by conditions such as temperature, storage and use, and refers owners to the vehicle and tire makers’ own recommendations, if any. All of them point to the date code as the way to find a tire’s age.

In Canada

Canada’s Motor Vehicle Tire Safety Regulations count the weeks slightly differently: week 01 is the week that begins on the first Sunday of the year, and the last two digits are the year in which that week begins.