I had a student in my office today, and we were trying to pinpoint the publication date of an advertisement. It was somewhere around the fifties, but we couldn't say late or early. To try and solve the puzzle I grabbed the phone and called an invaluable source of information on everyday life in Norway from 1940 and onwards - my mother. After five minutes of remembering when she had worked where, what she had sent home because of rationing in Norway while she was working in Sweden and what kind of clothes she had worn in Norway and in Sweden, we were a lot closer. We discussed briefly when eggs and flour, milk and butter became easily available in the stores, as well as female fashion: when the wide skirts came into fashion in Norway after the war - when material was abundant enough and the female profile changed to the wasp-waisted model-wife of the fifties.
The wonderful thing was that she could answer. I could get all this information easily and to the point, and in five minutes we had reduced the possible period for the advertisement from 18 years to 5. It never ceases to amaze me how much the people we take for granted know - the knowledge stored in living flesh, in vulnerable, decaying brains.