In the case of low production/exotic tires or those made overseas, it’s not unusual to find a new tire that’s already a year old.

Perhaps your tire has direction-sensitive treads or the tires were installed incorrectly to hide the tire manufacturing date. (I know, I always suspect foul play; it’s my nature.) ...

Sidewall inspection and date of manufacture deciphering are, admittedly, rule of thumb information. Where's the data to scientifically tell you the condition of your tires?