People in the United States set their clocks back at the end of Daylight Savings Time every year, which usually occurs in October or November. Not all countries in the world use Daylight Saving Time, but many do. It is most popular in the Western Hemisphere.
Similarly, people in countries that use Daylight Saving Time set their clocks forward an hour on a date in the spring. Daylight Savings Time was proposed in 1895 to promote more efficient use of daylight. It was first used in 1916 by Germany, and many countries followed suit. Not all countries shift their clocks by an hour; some use a 20- or 40-minute shift.