I never take any notice of sell-by dates on food. If it smells OK and doesn’t look putrid, then it’s OK to eat. So I’ve always reckoned.
So, lunchtime yesterday: I’m making myself a sandwich; I drag out an opened pot of carrot & parsnip veggie puree spread from the back of the fridge – haven’t had any for quite a while and I feel like a change; spread it on bread; start to eat.
Notice a tiny smudge of mould on the spread remaining in the pot; think, as always “Hah! Bit of penicillin never hurt anyone!”.
Continue munching.

OK, you can guess what happened later… Anyway, it wasn’t too bad – an afternoon and evening of bellyache, punctuated by visits to the toilet. No throwing up, not a lot of … well, you know what.
Sell-by date on the spread: 16th May. Spread now in bin, along with a couple of other packets of rather elderly spread.