GarageCalc 
How to find the code
Look for lettering that starts with DOT on the sidewall, followed by plant and
size codes, ending with four digits in a shallow oval. Manufacturers are only required to
put the full code on one sidewall, so if you see DOT followed by only partial characters,
check the other side of the tire.
How it's decoded
Reading 3422: a manufacture week, not an expiration date
The code 3422 means the 34th week of 2022. It does not mean March 4, 2022, and it does not give the day the tire was made. This tool uses an approximate week date to display age, so a month boundary can affect the displayed month. If the result is in the future, recheck that you entered the final four digits of the DOT marking.
Manufacture age also differs from time in service. A tire made in 2022 but first fitted in 2024 has two different clocks. Keep the purchase or installation record alongside the DOT code. Check all tires, including the spare: tires fitted together need not share a manufacture week.
Use age together with condition and manufacturer guidance
Michelin's tire-age guidance calls for annual professional inspections after five years of use and replacement ten years after manufacture, including spares. Follow any earlier limit specified for your vehicle or tires. A younger tire may still need replacement because of damage or wear.
This decoder cannot inspect cracking, bulges, pressure loss or internal damage. If you find a problem, arrange an inspection rather than treating a young date code as clearance to keep driving. NHTSA's tire safety guide explains tire identification, maintenance and aging considerations.
While you are at the sidewall, the other markings matter too: the load index and speed rating tell you whether the tire is even correct for the vehicle.
Frequently asked questions
Where is the date code on a tire?
At the end of the DOT marking on the sidewall: the last four digits, often in a recessed oval. It may appear on only one side of the tire, so you might need to check the inner sidewall. The first two digits are the week, the last two the year: 3422 means week 34 of 2022.
How old is too old for tires?
Follow your vehicle and tire manufacturers: an earlier replacement limit takes priority. Michelin recommends professional inspection annually after five years of use and replacement ten years after manufacture, including spares. Damage or wear can require replacement much earlier; a date code alone cannot establish safety.
My tire has a 3-digit date code. What does that mean?
Three-digit codes were used before the year 2000 (two digits for week, one for year). Any tire still wearing a 3-digit code is more than 25 years old and belongs in a museum, not on a vehicle.
Does tire age matter if the tread looks fine?
Yes. Tread depth alone does not establish tire condition. Aging, storage, heat, damage and use all matter. Check the manufacturer guidance and have a professional assess concerns even if the tread appears deep.