Sommartiden

Sommartiden, or daylight saving time, is the annual practice in Sweden and many European countries of advancing clocks by one hour to extend evening daylight. The change occurs during the warmer months, shifting daily schedules to better align daylight with typical activities.

In Sweden and most of the European Union, sommartiden begins on the last Sunday in March and ends on the last Sunday in October. On the start day, clocks are moved forward one hour, resulting in shorter mornings and longer evenings; on the end day, clocks are moved back one hour. Sweden uses Central European Time (CET, UTC+1) in winter and Central European Summer Time (CEST, UTC+2) in summer.

History and purpose: The concept gained wide adoption in Europe during the late 20th century, with harmonization in many countries to save energy and to make better use of daylight for work and leisure. The evidence on energy savings is mixed, and arguments against the practice include health effects, scheduling confusion, and disruption to sleep.

Regulatory status: In the European Union, the dates of sommartiden have been standardized, and there has been ongoing political discussion about ending seasonal clock changes and allowing member states to choose permanent standard time or permanent daylight time. As of now, no uniform abolition has been enacted, so the practice continues in Sweden and most EU countries.