It's not clear which credit you're referring to.
If it's Colorado's Innovative Motor Vehicle Credit, you can't claim the credit on a used vehicle. See Nonqualifying motor vehicles in the Colorado Department of Revenue's Income Tax Topics: Innovative Motor Vehicle Credit fact sheet.
If you're referring to the IRS' Used Clean Vehicle Credit, you can enter your vehicle's information in Federal Tax Credits for Pre-owned Plug-in Electric and Fuel Cell Vehicles to see if it qualifies for the credit.
As far as the relevant date, according to Previously Owned Clean Vehicle Credit in the Instructions for Form 8936 (2023):
The credit is equal to the lesser of $4,000 or 30% of the sales price of a previously owned clean vehicle you acquired and placed in service during your tax year.
[Bolding mine.]
See the IRS' Used Clean Vehicle Credit and Clean Vehicle Tax Credits for more information.
