Ready to lose an hour of sleep?

At 2 a.m. Sunday, people in 48 of the 50 United States and the western time zone of Indiana will move their clocks and watches ahead one hour to mark the change to daylight saving time. Residents in Arizona and Hawaii, Puerto Rico, the U.S. Virgin Islands and American Samoa will not follow the custom.

According to the website Time and Date.com, daylight saving time in the U.S. was introduced in 1918 when President Woodrow Wilson signed it into law to support the war effort during World War I.

The measure was repealed seven months later, although a few states hung on to the practice until President Franklin D. Roosevelt instituted year-round daylight saving time in the United States during World War II from 1942 to 1945.

After the war, the use of daylight saving time was scattered throughout the country until 1966, when Congress established the Uniform Time Act of 1966, which set daylight saving time from the last Sunday of April to the last Sunday of October.

The law allowed states to be exempt by state statute.

In 1974, Congress extended daylight saving time to 10 months and then reduced it to eight months in 1975 in response to the Arab oil embargo. While the move reduced fuel consumption, many complained about dark winter mornings and the danger to children going to school.

More recently, daylight saving time was extended to its present length — starting the second Sunday in March and ending the first Sunday in November —in 2007 after Congress passed the 2005 Energy Policy Act.