These codes are not difficult to read. They are difficult to find.
I have an Infiniti and a Nissan pickup. For each vehicle, the spare is a different make from the road tires, so I have 4 different makes of tires.
I just went out to check the dates, and in every case the date is on the inside of the tire, which makes it very difficult to see.
This is the spare of my Infiniti. It was made in week 37, so, September of 2015. Four year old tire, not bad for a spare.
They have been using the same code for at least the past 8 years. Obviously it is federally mandated because the numbers are all the same size, about 3/8 inch high.
My pickup spare tire, I just bought this one two months ago, manufactured January of this year.