Updating windows daylight savings
Members of the European Union conduct a coordinated shift, shifting all zones at the same instant, at Coordinated Universal Time (UTC), which means that it changes at Central European Time (CET), equivalent to Eastern European Time (EET); as a result, the time differences across European time zones remain constant.
North America shifts at but at the local time and is consequently uncoordinated - so that, for example, Mountain Time is, for one hour in the autumn, zero hours ahead of Pacific Time instead of one hour ahead and, for one hour in the spring, two hours ahead of Pacific Time instead of one hour ahead.
It became common during World War II, and was widely adopted in America and Europe from the 1970s as a result of the 1970s energy crisis.
Since then, the world has seen many enactments, adjustments, and repeals.
Most jurisdictions abandoned DST in the years after the war ended in 1918, with exceptions including Canada, the UK, France, Ireland, and the United States.It also acknowledged that private businesses were in the practice of changing their opening hours to suit daylight conditions, but they did so of their own volition.