What is the difference between short DST and long DST?

Daylight saving time (DST) refers to the practice of advancing clocks during warmer months so that darkness falls later each day according to the clock. The rationale behind DST is that it allows people to make better use of daylight hours by shifting waking hours. Many countries around the world observe DST, adjusting their clocks either one hour forward or backward depending on the time of year.

There are two main types of DST: short DST and long DST. Short DST involves advancing clocks by one hour during the summer months only. This is the system used by most of the United States and Europe. Long DST refers to remaining on summer hours all year without changing the clocks back in the fall. Some countries, such as Russia, observe year-round DST.

The key difference between short and long DST is the duration. Short DST lasts 4-8 months, while long DST is observed year-round without any time shifts. There are various arguments for and against both short and long DST.

What is DST?

Daylight Saving Time (DST) is the practice of adjusting clocks forward during the summer months to maximize daylight hours. According to the TechTarget definition, DST is the practice of turning the clock ahead as warmer weather approaches and back as it becomes cooler. The purpose of DST is to make better use of daylight hours by shifting sunlight into the evening. With DST, there is more light later into the evening, which conserves energy by reducing the need for artificial lighting.

According to TimeAndDate.com, DST involves setting clocks forward typically by 1 hour near the start of spring and then back again in the fall. This results in evenings having more daylight and mornings having less. The practice of DST has been around for over 100 years and aims to reduce electricity usage by aligning daylight hours with when most people are awake and active.

Short DST

Short DST typically refers to daylight saving time periods that are on the shorter end of the spectrum, lasting around 4-5 months per year. The most common short DST period lasts from late March through late October, shifting clocks one hour forward in the spring and back one hour in the fall (https://www.treehugger.com/do-we-still-need-daylight-saving-time-4863800).

Many regions in the Northern Hemisphere use a short DST period, including most of Europe, parts of North America, and some countries in the Middle East. For example, the European Union observes DST from the last Sunday of March until the last Sunday of October each year. The United States and Canada have a similar short DST period from mid-March through early November (https://www.assembled.com/blog/daylight-saving-time).

Proponents argue short DST provides extra daylight in the evenings during the spring and summer months, leading to energy savings, more time for leisure activities, and economic benefits for certain industries. However, critics say the biannual time changes disrupt sleep patterns and that any benefits are minimal.

Long DST

Long DST refers to Daylight Saving Time that lasts 8 or more months out of the year. Typically, Long DST starts in early March and runs through early November. This provides more evening daylight in the spring, summer, and fall compared to standard DST which runs from mid-March to early November [1].

In the United States, several states have passed legislation to adopt year-round or Long DST if Congress allows states to make DST permanent. These include Alabama, Georgia, Minnesota, Mississippi, Montana, Oregon, South Carolina and Tennessee. However, year-round DST has not yet been implemented anywhere in the U.S. [2].

Outside the U.S., areas that use Long DST include most of Saskatchewan in Canada, Namibia, and parts of Australia. In Saskatchewan, clocks move ahead by one hour on the second Sunday in March and remain on Long DST until the first Sunday in November [1].

Key Differences

The primary difference between short DST and long DST is the duration of the test. As the names suggest, a short DST is brief while a long DST is more extensive.

Specifically, a short DST typically takes just a few minutes to complete. It performs a basic check of the hard drive’s functionality. In contrast, a long DST can take hours as it does a much more rigorous examination of the drive [1].

In terms of impacts, a short DST uses fewer computer resources and less energy compared to a long DST. This makes short DSTs preferable in laptops to conserve battery life [2]. However, long DSTs provide a more comprehensive analysis of potential hard drive issues.

From a health standpoint, the extensive duration of long DSTs can lead to eye strain and headaches if monitoring the test progress. Short DSTs minimize these risks. Ultimately, the choice depends on balancing convenience and thoroughness.

Arguments For Short DST

One of the main arguments in favor of short DST is potential energy savings. The idea is that by having daylight hours better match people’s waking hours, less electricity will be used for lighting and heating homes and businesses. A study by the National Bureau of Economic Research found that during the 4 weeks of DST, electricity demand was reduced by 0.5% per day across the United States. They estimated national electricity savings of 1.3 billion kilowatt-hours, or the equivalent annual electrical use of over 100,000 households. Proponents argue that more sunlight in the evening reduces the need for artificial lighting (https://drivesaversdatarecovery.com/what-to-do-if-your-hard-drive-short-dst-check-failed/).

Arguments Against Short DST

One of the main arguments against retaining short DST year-round is that it provides less evening daylight. During the spring, summer, and fall months, sunset would come an hour earlier if short DST were used instead of longer DST. This means people would get out of work with the sun already setting or down, reducing opportunities for outdoor after-work activities. Shorter evenings could also impact the restaurant and tourism industries during peak seasons. According to one analysis, a national year-round adoption of permanent short DST could cost the leisure and hospitality industry over $7 billion in the first year alone (source).

Additionally, short DST does not properly match our natural circadian rhythms. Studies show that evenings with more daylight in the spring and summer months better match human wake/sleep cycles. The later sunsets of long DST in those seasons increase light exposure in the evening, which can help keep people alert and awake longer (source). This matches well with typical social schedules and allows more time for evening activities. In contrast, making short DST permanent could lead to increased sleepiness and disruption of circadian rhythms when sunset comes earlier.

Arguments For Long DST

Long DST provides up to a full extra month of evening daylight relative to the current system. Studies show that more daylight later in the day better matches most people’s circadian rhythms and natural sleep cycles. In research, Dr. Rachel Hopper states that “when we’re exposed to light in the morning, that actually advances our circadian rhythm so we wake up earlier, and when we’re exposed to light later in the day, it delays our circadian rhythm so we stay up later.” Therefore, the extra daylight in the evenings with year-round DST could improve health and sleep quality for many people.

Arguments Against Long DST

One of the main arguments against long DST is that it does not actually lead to significant energy savings. Some studies have found that while DST can conserve electricity used for lighting in the evening, it also increases electricity consumption in the morning. This is because people wake up before sunrise and use more electricity to start their day (1). Overall, the energy savings from long DST windows are minimal.

Another criticism of long DST is that it creates a mismatch between daylight hours and the clock time for several months of the year. In locations far from the equator, the sun may rise after 8am and set before 5pm during DST periods. This goes against the original intent of DST to align waking hours with available daylight. Having standard time better match solar time for more of the year is preferred by some experts (2).

In summary, two key arguments against long DST are less energy savings compared to claims and a disconnect between actual daylight and clock time for a portion of the year.


In summary, the key differences between short DST and long DST are the length of time they add daylight hours. Short DST shifts clocks ahead by 1 hour during the spring, summer, and early fall, adding daylight to the evening hours. Long DST shifts clocks ahead by 2 or more hours, maximizing daylight but also disrupting sleep cycles more. There are reasonable arguments on both sides for which option is better.

Arguments in favor of short DST typically focus on balancing benefits like energy savings, decreased traffic accidents, and more daylight hours after work with smaller disruptions to sleep cycles. Arguments against focus on the still present sleep disruptions and spikes in heart attacks and strokes after the spring shift. Those arguing for long DST emphasize maximum energy savings and daylight aligning more with waking hours. But arguments against long DST cite too much disruption to sleep cycles, more morning darkness, and trouble adjusting to 2+ hour time changes twice a year.

There are merits to both options, which is why the debate between short and long DST continues globally. The ideal approach likely depends on a region’s latitude, people’s work and lifestyle habits, and energy goals. While consensus remains elusive, the discussion helps ensure we periodically reevaluate if current DST laws make sense or need revisiting.