Daylight saving time is on the horizon. On March 12, most Americans will turn their clocks forward by one hour as the country begins its annual spring shift away from standard time. Adding extra sunlight to the day has its supporters and its detractors.

The impact of shifting more sunlight later into the evening on public health and safety has been the subjects of debate in recent years in light of efforts in Congress to make daylight saving permanent, but why do we have spring our clocks forward in the first place? 

Here’s why we have daylight saving time. 

Daylight saving time was ‘war time’ first    

Daylight saving time was first introduced in the United States in 1918 under the Standard Time Act as a measure to save on fuel costs during the First World War by adding an extra hour of sunlight to the day, according to the Library of Congress.

The United States followed the lead of several European countries at war that adopted daylight saving time during the summer months. Newspapers at the time reported that European countries had seen considerable savings in coal consumption.

The new law, signed by President Woodrow Wilson on March 19, 1918, also established a standard time and gave the federal government the authority to establish five different time zones across the county.

Daylight saving time was initially known as “war time,” according to the U.S. Department of Defense, because of its cost-saving purpose during the war. The U.S. abandoned daylight saving time at the federal level after the end of World War I, seeing no financial need, according to a Congressional Research Service report. States that wanted to continue observe the daylight saving locally had the option to do so.

The federal government would re-institute twice more daylight saving time on an emergency basis to conserve energy:

• Year-round daylight saving time was implemented during World War II
• Daylight saving time was extended from 1973 to 1975 during the oil embargo crisis. 

When did daylight saving time start?

The federal law that dictates daylight saving time as we know it today is the Uniform Time Act of 1966, which implemented a uniform time and date all states forwarded their clocks to observe daylight saving time. States were again given the option to not observe daylight saving time and remain on standard time. Two states: most of Arizona and Hawaii stay on standard time year round. 

Originally, daylight saving time began on the last Sunday of April and ended on the last Sunday of October, according to the Congressional Research Service. 

In 2005, Congress amended the Uniform Time Act to expand daylight saving time to the period in effect today: Starting on the second Sunday of March and ending on the first Sunday of November, according to the Congressional Research Service. This move was again for energy saving purposes. 

A Department of Energy study following the amendment’s implementation found the extra four weeks of daylight saving time saved around 0.5% in total electricity daily in the U.S., equaling energy savings of 1.3 billion kilowatt-hours annually. 

Efforts to make daylight saving time permanent

Dig Deeper

Contributing: Doyle Rice and Ashley R. Williams, USA TODAY