It's used part of an enormous Pavlovian experiment organised by secret government agencies and has been running as long as I can remember. Firstly a man shout "last orders" and rings a little bell which elicits the response of mass salivation and the intense desire to purchase as much booze as possible. These is then followed after a short but discrete pause by another bell and the cry of 'time', where upon individuals who, moments before looked like dehydrated camels now look sadly at the beverages and sip them like limp wristed nancy boys. All they while they are then harried by individuals with an ashtray in one hand who strides around saying things like "could you start drinkin up now", "do your talking while you walkin" and "I've got a home to go to too you know"
You could look at time as a concept invented by man, after all prehistoric people didn't have watches.
In the UK, knowing the time is a relatively new concept. During the Industrial Revolution people began to live by the clock instead of living by the seasons and the sun.
The introduction of trains made keeping track of time an important thing. It was then that Greenwich Mean Time was invented - to enable all of the UK to have the same time. Before that each town set their clocks by the sun and noon was slightly different the further east or west you went.