Kesäaikakäytäntö

Kesäaikakäytäntö, often translated as daylight saving time or summer time, is a practice of advancing clocks during warmer months so that darkness falls at a later hour of the day. The primary goal is to make better use of daylight. In many countries, clocks are typically moved forward by one hour on a specific date in the spring and moved back by one hour on a specific date in the autumn.

The concept of adjusting clocks to maximize daylight was first proposed by Benjamin Franklin in 1784, though his was more of a satirical suggestion. The modern idea was more seriously put forward by William Willett in 1907. Germany and Austria-Hungary were the first countries to implement daylight saving time nationally in 1916, during World War I, as a measure to conserve coal. Many other countries soon followed suit.

The effectiveness and benefits of daylight saving time are debated. Proponents argue that it saves energy, reduces traffic accidents and crime, and provides more opportunity for outdoor recreation in the evenings. Opponents contend that the energy savings are minimal or non-existent, that the change disrupts sleep patterns leading to health issues, and that the economic benefits are outweighed by the costs of implementation. Many countries have re-evaluated or abolished the practice in recent years.