An adult with normal habits who lives far from the equator will usually be asleep during several hundred daylight hours, almost all of these in the morning.
This weekend, 300m citizens of the European Union will turn the clocks back. A week later, 300m Americans will do the same. Adults are awake from 16 to 17 hours a day but it is light for only an average of 13 to 14 hours. So it is inevitable that we endure a thousand hours of darkness a year.
But we experience more darkness than necessary. An adult with normal habits who lives far from the equator will usually be asleep during several hundred daylight hours, almost all of these in the morning. Midday is not really the middle of anyone’s day. It is not even the middle of most people’s working day.
In traditional agricultural societies, people went to the fields at dawn and to bed when tired. Noon was when the sun was highest in the sky, so every location had its own time. But when populations began to work in factories and offices, hours of work were imposed on them. These regimes could not easily be varied from month to month.
The building of railways imposed further co-ordination. When Isambard Kingdom Brunel built a rail link from London to Bristol, his engineers would not allow the times at the ends of the line to differ by a quarter of an hour. Private initiatives to standardise time were subsumed by state control. In 1880 the British Empire, on which the sun never set, defined time zones for the world by reference to Greenwich Mean Time.
But why do our days make such inefficient use of daylight? We get more pleasure out of sleeping late and going to bed late than from the opposite and perhaps centuries of this bias have accumulated. Rich people always lived later in the day than poor people: they needed to wait till their shaving water had boiled and they could afford the light and heat needed to play cards into the night. Only in modern financial markets did many rich people feel obliged to begin work in the dark.
An Englishman, William Willett, drew attention to the inefficient use of daylight a century ago and proposed an ingenious solution. Now that governments controlled the time, they could make people turn their clocks forward or back. Willett’s campaign was quickly and unexpectedly successful. Summer, or daylight saving, time was adopted on both sides in the first world war.
The economic arguments were based on the implications of unnecessarily shortened daylight for industries such as farming and construction. Those arguments survived wartime exigencies. Today most places more than 30º latitude (Atlanta is 34º, New York and Madrid 41º, and London and Berlin 52º) shift clocks forward in summer.
Enforced time-shifting is an intrusive yet effective piece of economic and social engineering. Next week, even people free to rise when they choose, such as retirees and newspaper columnists, will get up later and go to bed later. Who would believe they could be induced to do this by government decree?
Effects on farming and construction are no longer important, but gaining more daylight saves energy used in lighting and heating. This was the main rationale for the extension this year of US daylight saving, which next week will upset transatlantic flight schedules and old computers. Most people prefer more daylight, even if the price is having to rise more often in the dark. Natural light was once more important to work than to leisure, but now many farms are golf courses and hiking trails. Modern play needs daylight; modern business does not.
Since the clock co-ordinates everyone’s activities, an efficient collective outcome cannot be reached through individual choices. Yet we have almost no evidence on public opinions or social consequences. The effects of policy are location-specific – the experience of Portugal (which briefly adopted Central European Time and regretted it) tells us nothing about the UK; the effects of the US experiment will be very different in Atlanta and Seattle. But for most places the balance of advantage points to turning clocks further forward and for longer. Yet next week 300m people will turn the clocks back, and many of them will consequently wake up in daylight and come home in the dark.