X2
I never visit the feed store without first reading the date. If any are old, I exclude those feeds from my choices.
Dates are either on the guaranteed analysis/ingredient tag or on the seal strip at either the top or bottom of the bag. Some are easily decipherable. Some use the Julian date.
ETA
Some stores are very good about moving product and dropping the price on feedstuffs starting to get old.
Some will keep it on the floor as long as it takes to sell.
I've seen feed a year or two old at some feed stores and other products like vitamins and electrolytes several years past the expiration date.
When I brought the expired vitamins to the attention of the merchant, they said, "OK".
Those packages are still on the shelf a couple years later.
When I questioned the age of feed when questioning a feed mill on the phone, they told me that grains last years. I said, "not after they have been ground".