Here is a 39-year-old version of the "McDreamy" star taking his enchanting looks to the lens during the ABC Upfronts back in 2005 (left). This was THE year he started playing and slaying as Dr. Derek Shepherd on "Grey's Anatomy."

And, 18 years later the handsome actor was looking suave on the streets of NYC where he was recently doing press for his current starring role in "Thanksgiving" (right) ... Dempsey plays the town's hot sheriff alongside Addison Rae.

Giving thanks to ALL the good looks PD continues to bless us with ...

The question is ...