Any tire used on U.S. roads must display a DOT (Department of Transportation) code on its sidewall. This code confirms that the tire complies with safety standards set by the U.S. Department of Transportation. Even in many countries outside the U.S., tire manufacturers follow the DOT marking system to ensure consistent global safety and traceability.

What Is a DOT Code / Tire Identification Number (TIN)?
The DOT code, also called the Tire Identification Number (TIN), always begins with the letters “DOT” followed by a combination of 8 to 13 characters. These characters hold specific information: the factory where the tire was manufactured, the tire size, its construction type, and most importantly, the date of manufacture.

For example, let’s break down this DOT code: FD AP LJO 4518.

• The first two letters, FD, identify the manufacturing plant. In this case, “FD” is assigned to the Yokohama factory in Japan.
• The next two characters, AP, represent the tire size code.
• The next three, LJO, indicate the tire type code.
• The last four digits, 4518, are the date code, showing that the tire was made in the 45th week of the year 2018.

What Is the DOT Date Code?
The date code is always the last 4 digits of the DOT number. It tells you the week and year the tire was made. The first two digits represent the week number, and the last two represent the last two digits of the year. For instance, 0118 means the tire was produced in week 1 of 2018.

Understanding how weeks are counted

Understanding how weeks are counted is important. According to DOT rules, the first week of the year is the first full calendar week—meaning it starts with the first Sunday of the year and ends on the following Saturday. If January 1 falls midweek, that partial week does not count as Week 1. Instead, Week 1 begins with the next Sunday.

The calendar week always runs Sunday through Saturday. The last week of the year may sometimes include up to six days of the following year, but never more. For example, if December 31 falls on a Wednesday, then that week counts as the last DOT week of the year—even though it carries over into January.

53rd Week of an Year

In the DOT (Department of Transportation) week system, a year has 53 weeks only if it starts on a Sunday or ends on a Sunday. Between 2000 and 2030, the following years have 53 weeks:

2000, 2006, 2012, 2017, 2023, and 2028

These years meet the criteria because either January 1st falls on a Sunday, or December 31st does — creating room for an extra full calendar week (Sunday to Saturday)

Why Week 53 Tires May Include Days from the Next Year

The 53rd week can partially include calendar days from the next year because the DOT week runs from Sunday to Saturday. So, if the 53rd week starts on the last Sunday of December, it will spill over into early January of the following year.

For example, if Week 53 of 2023 starts on Sunday, December 31, 2023, and runs through Saturday, January 6, 2024, some of those production days fall in the new calendar year (2024).

However, the DOT date code will still show “5323” because the week is counted as the 53rd week of 2023, even though the actual calendar days include some days in 2024.

So yes — some tires marked with a Week 53 date code are physically produced on calendar days of the next year, but for labeling and traceability, they belong to the previous year’s production batch.