Tire date code decoder: how old is my tire?

Where to find the date code

Look for the letters DOT on the sidewall. The group of characters after them is the tire identification number (TIN), and its last group is the date code.

“The date code, consisting of four numerical symbols, is the final group. The date code must identify the week and year of manufacture.” [49 CFR 574.5]

On radial tires for cars, SUVs and light trucks made on or after September 1, 2009, federal Standard No. 139 puts the full number on the side meant to face out; the other side may show the number without its date code:

“Tires manufactured on or after September 1, 2009. Each tire must be labeled with the tire identification number required by 49 CFR part 574 on the intended outboard sidewall of the tire.” [49 CFR 571.139]

That standard covers these tires:

“This standard applies to new pneumatic radial tires for use on motor vehicles (other than motorcycles and low speed vehicles) that have a gross vehicle weight rating (GVWR) of 10,000 pounds or less and that were manufactured after 1975.” [49 CFR 571.139]

So if the code you find ends without four digits, turn to the other sidewall. On a mounted tire the date may face the car; a shop can show it to you.

How to read the four digits

The first two digits are the week, the last two the year. The rule counts weeks in a particular way:

“The first and second symbols of the date code must identify the week of the year by using “01” for the first full calendar week in each year, “02” for the second full calendar week, and so on. The calendar week runs from Sunday through the following Saturday. The final week of each year may include no more than six days of the following year.” [49 CFR 574.5]

“For example, 0109 means the tire was manufactured in the first full calendar week of 2009, or the week beginning on Sunday, January 4, 2009, and ending on Saturday, January 10, 2009.” [49 CFR 574.5]

Some example codes, worked out with the same rule (week 01 starts on the first Sunday of the year):

Tires made before July 2000: three digits

Until July 2000 the date group had three symbols, and the last one gave only the last digit of the year:

“The first two symbols identify the week of the year, starting with “01” to represent the first full week of the calendar year, and the third symbol represents the year. For example, “218” would represent the 21st week of 1998.” [Tire Identification and Recordkeeping; Tire Identification Symbols (final rule)]

“Effective July 2, 2000, the number of digits in the date code will be increased from 3 to 4, the first 2 digits representing the week of manufacture and the last 2 digits representing the year of manufacture.” [Tire Identification and Recordkeeping; Tire Identification Symbols (final rule)]

The agency explained the reason for the fourth digit in a later rule:

“require the date of manufacture to be expressed in four digits, instead of the previously required three, so that consumers would be able to determine the decade of manufacture of their tires” [Certification; Federal Motor Vehicle Safety Standards; Tire Identification and Recordkeeping; Consumer Information Regulations]

A tire with a three-digit date code was made before mid-2000. Tire makers were allowed to switch to four digits early:

“Optional early compliance is permitted, commencing on the date of publication of this final rule in the Federal Register.” [Tire Identification and Recordkeeping; Tire Identification Symbols (final rule)]

The rule was published on July 8, 1999, so a four-digit code ending in 99 comes from the second half of 1999, and a four-digit code ending in 98 or earlier does not exist. The decoder reads a code such as 3099 as week 30 of 1999.

The rest of the code

A new tire's TIN has 13 symbols [49 CFR 574.5]: a three-symbol plant code that identifies the maker or retreader (NHTSA assigns it), a six-symbol manufacturer's code, and the four-digit date code.

“A manufacturer may continue to use a previously assigned two-symbol plant code until April 13, 2025.” [49 CFR 574.5]

A used tire made before that date may carry the older, shorter TIN that makers with a two-symbol plant code (and retreaders) could use until then [49 CFR 574.5]. In that format:

“The plant code, consisting of two symbols, must be the first group of the TIN.” [49 CFR 574.5]

“For new tires, the second group, consisting of no more than two symbols, must be used to identify the tire size.” [49 CFR 574.5]

“The third group, consisting of no more than four symbols, may be used at the option of the manufacturer or retreader as a descriptive code for the purpose of identifying significant characteristics of the tire.” [49 CFR 574.5]

The date code is still the last four digits. For example, a code written as DOT EJ HC 7HY 1210 (an illustration of the format, not a particular tire) has the plant code EJ, the size code HC, the optional code 7HY and the date code 1210: week 12 of 2010. The decoder reads either format, because it looks only at the last group. Type the groups with spaces between them, as they appear on the tire: on an old tire whose optional code ends in a digit, that keeps a three-digit date code (such as the 123 in DOT EJ HC 7H9 123) from being read together with that digit.

A retreaded tire carries a shorter TIN (seven symbols: the retreader's plant code and a date code) and an extra mark:

“The symbol “R” must be used to identify retreaded tires” [49 CFR 574.5]

The rule also limits the characters that can appear, which helps when a worn sidewall is hard to read:

“The only symbols that manufacturers and retreaders are allowed to use in the tire identification number are: A, B, C, D, E, F, H, J, K, L, M, N, P, R, T, U, V, W, X, Y, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 0.” [49 CFR 574.5]

There is no G, I, O, Q, S or Z in a TIN, so a character that looks like an O is a zero, and one that looks like an S is a 5. The decoder points out any character the rule does not allow.

How old is too old? What tire makers say

The federal rule that requires the date code does not set an age at which a passenger tire must be retired. Tire makers publish their own guidance. Michelin:

“After five years of service, tires should be thoroughly inspected at least once a year by a trained tire professional.” [Michelin tire age]

“As a precaution, Michelin recommends replacing tires ten years after their date of manufacture, regardless of remaining tread depth or apparent condition. This recommendation includes spare tires.” [Michelin tire age]

Bridgestone, for its Bridgestone and Firestone tires:

“Bridgestone recommends that its Bridgestone or Firestone brand tires be removed from service after ten years regardless of their remaining tread depth.” [Bridgestone tire life]

“If any tire is older than 6 years and shows aging, ask a tire expert.” [Bridgestone tire life]

The decoder sets the age it reads against these lines:

Two cautions on a used tire. Michelin's five-year line counts years of service; a used tire's time in service is unknown, but it cannot be longer than the tire's age, so the decoder shows the line against the age. And the decoder measures the age from the Sunday that starts the date-code week, the earliest day the tire can have been made, so it never understates it.

Worked example

A used tire marked 2219 was made in week 22 of 2019, the week of June 2, 2019 to June 8, 2019. Read on June 1, 2027 (a date chosen for the example), it is 7 years, 11 months old: past Michelin's five-year inspection line and Bridgestone's six-year line, with the ten-year line on June 2, 2029 for both makers.

What the date code does not tell you

The date says nothing about how the tire was stored, driven, repaired or damaged. When you buy a used tire, check the date along with the tread depth and the condition of the tread and sidewalls; our used tire checklist lists what the federal and state rules look for, and the tread depth chart converts a gauge reading.