What Is Daylight Saving Time?

What is daylight saving time?

Daylight saving time, often abbreviated DST and casually called daylight savings, is the practice of setting clocks forward by one hour during the warmer part of the year, then back again in the cooler months. The effect is to shift an hour of daylight from the early morning, when many people are asleep, to the evening, when they are awake to enjoy it. The change is easy to remember with the phrase spring forward, fall back: clocks move forward one hour in spring and back one hour in fall. During the period when clocks are advanced, a location is on daylight saving time; the rest of the year it is on standard time. Not all countries or regions observe it.

Why do we have daylight saving time?

The main rationale for daylight saving time is to make better use of natural daylight during the longer days of spring and summer. By shifting the clock forward, sunset happens an hour later in the evening, giving people more usable daylight after work for outdoor activities, and reducing the need for artificial lighting in the evening, which was historically framed as an energy-saving measure. The idea has been implemented in various forms for over a century. Its actual benefits, particularly the energy savings, are debated, and daylight saving time has become controversial, with ongoing discussions in some places about whether to keep it, abolish it, or make one time permanent. For now, though, it remains in effect across many countries.

When does daylight saving time happen?

The exact dates differ by country and region, which is part of what makes it confusing for travelers. In the United States, daylight saving time typically begins on the second Sunday in March, when clocks spring forward, and ends on the first Sunday in November, when they fall back. In Europe, the change happens on the last Sunday in March and the last Sunday in October, so the US and Europe shift on different dates, creating a few weeks each year when the usual time difference between them is temporarily off by an hour. In the Southern Hemisphere, where seasons are reversed, the shifts occur at opposite times of year. Many countries near the equator and some regions do not observe daylight saving time at all.

How does daylight saving time affect travel?

For travelers, daylight saving time can cause scheduling confusion, so it is worth being aware of. If your destination observes DST and your home does not, or if the two change on different dates, the time difference between them can vary from what you expect, which matters for booking flights, catching connections, and calling home. On the day of a time change, clocks shift by an hour overnight, so check that your devices update correctly and that any early departures account for the change. Some regions do not observe DST, so a country that is normally a set number of hours ahead may temporarily be an hour different. When traveling around the change dates, double-check local times for your flights, tours, and appointments to avoid being caught out by the shift.