This is the first of two annual time changes—one that some dread because it disrupts sleep and daily routines, while others welcome because of the longer evenings spent outdoors.

Regardless of opinion, daylight saving time is an age-old practice with a long history — but will it last? While some lawmakers have pushed to eliminate it, no law has been passed to make a change.

Here’s what to know about the biannual time change, including its start and end dates, history, and why it still exists.

Englishman William Willett was the first to start the daylight savings time movement

Willett was horseback riding one morning and suggested that clocks move forward more than 80 minutes so that United Kingdom residents could enjoy long days outside. For years, he championed the idea with a published brochure and verbally spoke about it, but he later died in 1915 at age 58 without witnessing his concept come to realization, according to History.com.

A year later, Germany became the first country to implement daylight saving time during World War I on April 30, 1916. The two European countries were considered wartime enemies, but the United Kingdom began using the practice several weeks later, per History.com.

Despite past remarks, American farmers did not champion daylight savings time to gain extra daylight hours to work in the field. They were completely against it after it was first observed as a wartime measure on March 31, 1918.

“The sun, not the clock, dictated farmers’ schedules, so daylight saving was very disruptive. Farmers had to wait an extra hour for dew to evaporate to harvest hay, hired hands worked less since they still left at the same time for dinner and cows weren’t ready to be milked an hour earlier to meet shipping schedules,” according to History.com.

USA Today reported that daylight savings time was reimplemented during the Uniform Time Act of 1966 when the nation’s time zones were standardized.

When does daylight savings time start?

Daylight savings time begins on Sunday, March 9, at 2 a.m. local time.

What is daylight savings time?

Daylight savings time is the eight months between March and November, during which most Americans lose an hour as clocks spring forward to produce longer summertime evenings. Blavity reported that the vernal (or spring) equinox represents the first day of spring, which falls on March 20.

When does daylight savings time end?

Daylight savings time ends on Sunday, Nov. 2.

Only two states do not observe daylight savings time

Hawaii and most of Arizona (with the exception of the Navajo Nation) are the only states that do not observe daylight savings time. Instead, they operate at a regular standard time, according to USA Today.