DOT Tire Date Code
Authority: U.S. DOT / NHTSA 49 CFR Part 574.5
The DOT date code is the final four digits of a tire's Tire Identification Number, molded into the sidewall. The first two digits give the week of manufacture (01-52) and the last two give the year, so '2318' means the 23rd week of 2018. Tires made before 2000 used only three digits, leaving the decade ambiguous.
| Parameter / Specification | Standard Value | Unit |
|---|---|---|
| Current Code Length | 4 | digits |
| Week of Manufacture (digits 1-2) | 01-52 | week of year |
| Year of Manufacture (digits 3-4) | Last two digits of year | - |
| Example Code: 2318 | 23rd week of 2018 | - |
| Pre-2000 Format | 3 digits (week + single year digit) | decade not indicated |
Reading the DOT Date Code
The date code is the last group of characters in a tire's Tire Identification Number (TIN), the string molded into the sidewall near the DOT marking. Under 49 CFR Part 574.5, the date code consists of four numerical symbols: the first two identify the week of the year, and the final two give the last two digits of the manufacturing year. A TIN ending in '2318', for example, indicates a tire built in the 23rd week of 2018.
Because tires degrade with age even when tread wear looks minimal -- rubber compounds oxidize and stiffen over years of heat and UV exposure -- the date code is the standard way to check how old a tire actually is, independent of how much tread remains or how the tire was stored.
The Pre-2000 Three-Digit Code
Before 2000, the date code portion of the TIN used only three digits rather than four: two for the week and one for the year. That single year digit meant a code like '042' could represent the fourth week of 1982, 1992, or any other decade ending in the same digit, with nothing in the code itself indicating which decade was meant. Determining the true age of an older tire required cross-checking other markings or documentation rather than reading the date code alone.
The switch to a four-digit code removed that ambiguity going forward, and it's a useful reminder when buying used tires: a three-digit code is itself a signal that the tire is at least a couple of decades old and warrants close inspection or replacement regardless of visible tread depth.