I checked with a shop a year ago about tire dates. He said they didn’t want to mount a tire over 7 years old. Yes there can be exceptions, also vary by shop & tire use. Just posting what this shop said about dates.
You're correct on the date of manufacture. I know Discount Tire won't touch a tire over 10yrs old for rotation/balance and starts suggesting replacement when older 6yrs. Personally for me if its over 8 years old I'm pretty leary of them and I won't ride on anything over 10yrs old no matter how good it may look.