The idea of putting the clocks forward in spring and back in autumn was not new when the First World War broke out. Benjamin Franklin had suggested it in a letter to The Journal of Paris in 1784. Candles were wasted in the evenings of summer because the sun set before human beings went to bed, he said, and sunshine was wasted at the beginning of the day because the sun rose while they still slept.
It was the First World War that secured the change. Faced with acute shortages of coal, the German authorities decreed that on 30 April 1916, the clocks should move forward from 23:00 to midnight, giving an extra hour of daylight in the evenings. What started in Germany as a means to save coal for heating and light quickly spread to other countries.
Britain began three weeks later on 21 May 1916, passing daylight saving time (known as British Summer Time) under the Defence of the Realm Act (DORA), as a way of improving the productivity of the workforce. Other European countries followed. On 19 March 1918, the US Congress established several time zones and made daylight saving time official from 31 March for the remainder of the First World War.