When I was a student, my housemates and I would buy our groceries from a shop that offered only days of the week as the best before. We had a lettuce that went off on ‘Tuesday’, bread that would go stale on a ‘Thursday’, and so on. It was useful for the shop, and useful for a bunch of cash-strapped students as we could effectively decide which Tuesday the food would spoil by, rather than throwing it out.