How is the 10-year period for DUI convictions measured?

The 10-year period is measured from the date of violation/offense, not from the date of conviction.¹

For example, you were arrested for a first DUI on September 1, 2008, but you went to court and eventually pleaded guilty or no contest on January 1, 2009. If you get another DUI 10 years from the date of offense (September 1, 2008), you will be charged with a DUI and also with a sentence enhancement that accuses you of having a prior DUI.

DUI convictions stay on your record for more than 10 years. It is common for prosecutors to use DUI convictions older than 10 years to argue for increased punishment and to set bail.

For commercial license holders, there is no limit to how far back the DMV or the court can look back to see when you got a prior DUI or DUI license suspension to disqualify you from operating a commercial vehicle.