The curse of 'Use By' dates

News that we are throwing out 15% of the edible food we buy comes as no surprise to me. For years I have been banging my head against the immutable views of, er, a person close to me that 'use by' dates on food packaging are prescriptive.

How is it that something that's fine to eat at ten to midnight suddenly becomes poison a minute after twelve and must be consigned to the bin as soon as its 'use by' date rolls up?

"Better safe than sorry" usually comes the reply.

"Well, when your mother went into hospital I ate nothing but food past its sell-by dates bought for 50p from the supermarket; I'm still here, aren't I?"

The usual sotto voce reply of "worst luck" doesn't encourage me that I'm making much progress on this one.