Does the 10 year window start from the first offense date or the conviction date?

I recently was charged with DUI on May 21,2017. I have a previous DUI from December 14, 2006. The conviction date was August 8, 2007. I'm hoping the offense date because it wouldn't seem fair from the conviction date, since I have no control over how long it takes to go to court. Essentially, I would be losing those 8 months from when it initially occurred.