Born Date

The SPD on the fender tag is just when the factory "planned" on building the car. Most of the time, the vehicle was NOT built on that day.

Sometime in 72, the door stickers were changed and an MDH code was added to them. My 73 Challenger has an SPD of 927(September 27th) however, the MDH code says 101212.(door sticker says 10-72) The car was built 2 weeks after its SPD.

If you have an earlier 72 or older car without an MDH code on the door sticker, there is no way to know the exact date the car was completed.
It is possible to get close, if not the day. If you have your original build sheet with the Inspectors Initials on it, then that was the day the sheet was put wherever they put it. In 1967 and 68, if you look at the top of the sheet,you have the sequence number, second box is build date, third is the
shipping number. My 67 GTX has a build date of 5-16 on the fender tag, and a code of 516 on the build sheet, with the Inspectors Initials on it.
My 68 charger has a build date of A22 on the tag, and A23 on the build sheet. The warranty card issue to the buyer was November 67, as it was an ordered car, and picked up upon delivery.