The chronological age of any tyre can be found on the tyre sidewall by examining the characters following the symbol "DOT". The last four numbers identify the date of manufacture of the tyre to the nearest week. The first two of these four numbers identify the week of manufacture (which range from "01" to "53"). The last two numbers identify the year of manufacture (e.g., a tyre with the information "DOT XXXXXXX2714” was manufactured in the 27th week of 2014).
For tyres manufactured prior to the year 2000, three numbers instead of four indicate the date of manufacture. Also, during the early 1990’s, Continental added a triangle (◄) to the end of the character string to distinguish a tyre built in the 1990’s from previous decades (e.g., a tyre with the information "DOT XXXXXXX274◄” was manufactured in the 27th week of 1994).
All tyre (including spare tyres) that were manufactured more than ten years ago should be replaced with new tyres, even if they appear to be usable from their external appearance and if the tread depth may have not reached the minimum wear out depth.