For most of history most people have lived by the celestial clock of night and day, and by the biological clock of hunger and thirst. But with civilisation came the astonishing idea that the day might be divided and sub-divided into regular units of time. Here then are the hours, from dawn to Eliot's "uncertain hour before dawn" by way of elevenses and the lunch hour, the hours for siesta and for tiffin, vespers and the witching hour.
