Why is it that instructions often say 'Best before end June', rather than 'Best before July'?
A more precise instruction might say 'Best before July, very good before August, still OK before September, but may have gone off by October'.
When going through those cupboards, or fridge, searching for 'out of date' foods, it might simply be wise to look for packaging offering a 'Chance to win a Sinclair C5, or Tickets to the World Cup Final in Mexico'. These are a good hint.
Other serious signs include seeing the price marked in pounds, shillings, and pence; or even a nasty pong!
I hope this has been of help.