That's actually a very useful heuristic because, unlike perhaps in the US, in many parts of the world food standards even in higher quality restaurants are rather lax.
Even in the US I learned the hard way about eating lunch early. Chipotle is perfectly fine with serving old steak from yesterday if you're one of the first customers of the day.
I was told once that Wendy's chili is made from the hamburgers that weren't sold the day before. I don't know if it's true or not, though. Even if it is, that's some fine chili for a chain fast food restaurant.
