I was planning to cook chicken tonight... until I noticed that it said sell by yesterday's date. Would it still be okay to use today or does sell by = use by?
You can usually use it for a few days past the sell by date. A lot of times I buy meats discounted to use within the next week because it is the exipration date that day ro the next.
DW is a food scientist, so she could give a more precise answer, but, assuming that the chicken was sealed, unopened, and had been properly stored, you are fine with using it. I'm pretty sure that you have anywhere from a couple days to several weeks (or more!) past the sell-by date before you have to worry about the food going bad.
I had this happen to me last night and called our local butcher. He said "most stores" will put a sell by date on it with the expectation that it is used no more than 3 days later...sometimes as many as 7.
Sell by is fine if it was properly refridgerated. I wouldn't if it was 3 + days past that date.
I also go by look/smell because I don't care what the date is if it looks or smells bad. Sometimes stuff goes off before the date, other times it's great well past the date.