Who decides when daylight savings time begins?

Answer 1

The individual country's legislatures. In the United States, the US Congress (House and Senate) pass a bill. The President of the US signs it into law.

Answer 2

Daylight saving time begins and ends on dates established by legislation in each country or region. Typically, a governing body, such as a country's Congress or Parliament, will pass a law specifying the start and end dates of daylight saving time. In the United States, for example, Congress passed the Uniform Time Act in 1966, which established the rules for when daylight saving time begins and ends.