Set to expire this weekend, Daylight Saving Time is scheduled to end Nov. 2 at 2 a.m. and return most watches and clocks in the United States back to Standard Time.

Every spring, clocks are moved one hour ahead and then moved back again in the fall, hence the phrase “Spring forward, fall back.”

The change to Daylight Saving Time is meant to encourage conservation of energy by using less of it in lighting homes and taking advantage of the longer and later daylight hours during the summer months.

Lawmakers occasionally tinker with the exact date and states that actually observe the time change, last altering the law in 2005 to extend the period by four weeks. Daylight Saving Time now runs from the second Sunday of March to the first Sunday of November, is expected to save 10,000 barrels of oil each day.

Notably, a few U.S. states and territories ignore Daylight Saving, including Arizona (except some Indian Reservations), Hawaii, Puerto Rico, the U.S. Virgin Islands, and American Samoa. Due to their proximity to the equator, the amount of daylight in these places are more consistent in length throughout the year. All of Washington State observes Daylight Saving Time.