What Is the Point of Daylight Saving Time?

First, let's explore where this all started in the first place. In this case, it all goes back to one of the U.S.'s founding fathers: Benjamin Franklin.

He first conceived the idea of daylight saving time (DST) in 1784 while serving as the U.S. ambassador to France. He observed that many Parisians slept through sunlit hours and used candles well into the evening and pondered (perhaps a bit jokingly) if adjusting schedules to align with longer summer days would conserve tallow and wax.

Though he whimsically suggested using cannons to wake people early, it's believed he was jesting with his audience. Despite introducing the idea in an article, Franklin didn't further pursue DST. It took more than a century before DST received serious consideration as a practical timekeeping method.

Now let's look at how daylight saving time works and what happens when we "spring forward" and "fall back."

DST delivers the most benefits when the days are long, as they are during summer. If you recall from your high school Earth science class, seasons are reversed in the Northern and Southern Hemispheres. When it's summer in North America, it's winter in South America and vice versa.

That means DST rules must also be reversed.

In the Northern Hemisphere, DST starts in the spring — typically between March and April — and concludes in the fall — between September and November. In the Southern Hemisphere, DST begins between September and November and ends between March and April.

These start and stop dates are completely arbitrary, but over the years, most countries have adopted similar guidelines. The United States follows rules established by the Energy Policy Act of 2005. According to that legislation, daylight saving time begins in the U.S. (a country in the Northern Hemisphere) at 2 a.m. on the second Sunday in March.

That's when many Americans move their clocks forward by one hour and, if they're diligent citizens, replace their smoke detector batteries. It ends about eight months later; at 2 a.m. on the first Sunday in November, clocks move back an hour and standard time reigns again.

Rules and Regulations

Although the U.S. Energy Policy Act thoughtfully provides rules to standardize the implementation of daylight saving time, it doesn't require all states to follow them. In fact, any state or territory can apply for an exemption and, if it's granted, sidestep DST and remain on standard time throughout the year.

Hawaii, American Samoa, Guam, Puerto Rico, the U.S. Virgin Islands and most of Arizona (with the exception of the Navajo Indian Reservation) all chose this option. Indiana, which used to observe DST in only 15 of its 90 counties, now "springs forward" and "falls back" across the whole state.

Don't think Americans are alone in their zeal to stretch out summer days. Since its introduction, at least 66 countries have practiced DST, but some later abandoned it for various reasons.

European nations have been taking advantage of what they call "summer time" for decades, but they didn't standardize it until 1996, when the European Union adopted a common DST schedule that runs from the last Sunday in March through the last Sunday in October.

Regardless of the specific rules implemented by a country, starting and stopping DST works the same way. A popular start time is 2 a.m., because most people are zonked out, and most businesses are closed. At that time, the clock moves forward exactly one hour. Here's a second-by-second account of what occurs:

1:59:58 — It's standard time.

1:59:59 — Yep, still standard time.

3:00:00 — We're on daylight saving time now.

3:00:01 — Daylight saving time rocks on for the next few months.

Notice that every second between 2:00:00 and 2:59:59 disappears completely. To start DST, a full hour must be skipped! In the fall, when daylight saving time ends, you get the lost hour back because the time from 1:00:00 to 1:59:59 is repeated for one day. Here's what it looks like:

1:59:58 — Daylight saving time still rules.

1:59:59 — DST's last hurrah.

1:00:00 — Standard time has assumed command.

1:00:01 — Standard time rolls on until the next time ...

Notice that the clock moves from 1:59:59 to 1:00:00, not 2:00:00. In other words, one full hour occurs twice, and the day ends up being 25 hours long.

Most people don't ever need to refer to time within this hour, but if they do, say, because a birth or death occurred, they need to mention whether it was before or after the change back to standard time.

It's taken a few years — and several changes — to perfect this time-switching model.

We know how it works, but why was daylight saving time created? Simply put, the practice of setting the clocks forward by one hour during warmer months to extend evening daylight allows people to make better use of natural daylight.

This shift reduces the need for artificial lighting in the evenings and decreases energy consumption, promoting energy conservation and allowing us to advantage of longer daylight periods during spring and summer.

However, its actual energy savings and broader impacts remain debated. While many countries observe DST, others have abandoned or never adopted it, citing minimal benefits or disruptions to routines.

The concept of DST dates back to ancient civilizations, where daily schedules were adjusted based on the sun. The idea of modern DST was first proposed in 1895 by George Hudson, an entomologist from New Zealand, who wanted more evening light for insect collection. British builder William Willett later championed the idea in 1907 to reduce daylight wastage.

DST gained traction during World War I, with Germany adopting it in 1916 for energy conservation. Many countries, including the U.S., followed. Its use persisted during World War II for similar reasons. The U.S. sought to standardize DST with the Uniform Time Act in 1966, setting its observance from the last Sunday in April to the last Sunday in October.

However, in response to the Arab oil embargo, the U.S. wound up observing year-round DST in 1974 and 1975, sometimes referred to as periods of "permanent" daylight saving time.

A little over a decade later, former President Ronald Reagan adjusted DST's start to the first Sunday in April in 1986. Then, in 2005, President George Bush extended DST from the second Sunday in March to the first Sunday in November, effective from 2007. That year, Indiana also standardized its DST observance.

Today, DST is practiced in over 70 countries, impacting billions. While its energy-saving benefits are debated, some regions have opted out due to health concerns.

DST has been debated for decades. Here are the main arguments supporting DST:

Here are some of the counterarguments against DST.

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.