What is a long DST check?

A long DST check refers to adjusting clocks for Daylight Saving Time (DST) in the spring when clocks move forward by one hour. The “long” check indicates it takes longer to complete compared to the “fall back” DST change in autumn.

Some key questions about long DST checks include:

When does the long DST check happen?

The long DST check occurs in spring, typically in March for most of the United States. The exact date varies by country and region.

Why do we have a long DST check?

DST was originally implemented to save energy and make better use of daylight hours. The biannual clock changes aim to provide extra evening daylight in summer while still allowing normal sunrise times in winter.

How does the long check work?

During the long check, clocks shift forward one hour from 2:00AM to 3:00AM local time. This pushes an hour of daylight from the morning to the evening. Sunrise and sunset will be one hour later compared to standard time.

What areas observe DST?

Most of the United States, Canada, Europe, Australia and parts of South America and Asia observe DST. Not all areas or countries participate, such as most of Africa, the Middle East, China, Japan and India.

When and Where Does the Long DST Check Occur?

As mentioned above, the long Daylight Saving Time change occurs in spring, usually in March for most parts of the United States and Canada. The exact date and time varies by region:

  • In the U.S., the change occurs on the second Sunday in March at 2:00AM local time.
  • In Canada, it occurs on the second Sunday in March at 2:00AM local time.
  • In the European Union, it is the last Sunday in March at 1:00AM UTC.
  • In the UK, it is the last Sunday in March at 1:00AM GMT.
  • In Australia, it varies by state, occurring in October or early November at 2:00AM local time.

So in summary, for most of the U.S. and Canada, expect the change to happen on the second Sunday in March. Adjust your clocks forward one hour at 2:00AM local time on that date.

The History Behind Daylight Saving Time and the Long Check

Benjamin Franklin first conceived the idea of Daylight Saving Time in 1784 as a way to save on candle usage and make better use of daylight hours. However, it was not implemented for over a century after that.

Germany and Austria were the first to establish DST in 1916 as a wartime effort during World War I. The goal was to conserve fuel and resources for the war by aligning daylight hours with typical waking hours. Other countries soon followed, including the United States in 1918. It was repealed after the war ended.

During World War II, DST was reestablished by many countries, again to save resources for the war. The United States made it a national standard in 1942. After the war, individual states could choose whether to observe it or not, causing confusion.

The Uniform Time Act of 1966 standardized DST dates across the U.S. and made observing DST mandatory for states (they could only opt out of it by passing state legislation). This helped avoid disruption in transport, communications and commerce by ensuring consistency.

The current DST schedule was established with the Energy Policy Act of 2005, which extended the duration of DST starting in 2007. Today, DST aims to conserve energy, align waking hours with daylight, and reduce traffic accidents.

Key Dates in DST History

  • 1784 – Benjamin Franklin first proposes concept of DST
  • 1916 – First established by Germany and Austria during World War I
  • 1918 – United States implements DST for the first time
  • 1942 – DST made a national standard in the U.S. for WWII
  • 1966 – Uniform Time Act creates consistency in DST observance
  • 2007 – Current DST schedule implemented in U.S. and Canada

The Purpose and Goals of the Long DST Check

Shifting clocks forward by one hour during the long DST check serves several purposes:

Maximizing Daylight Hours

By starting the day’s clock one hour earlier, more usable daylight occurs in the evening, aligning with typical waking hours.

Saving Energy

More daylight in the evening reduces the need for artificial lighting. This conserves electricity and lowers energy demands during peak usage times.


The extra hour of evening light potentially reduces traffic accidents by making driving conditions better in the evening.

Economic Impacts

DST affects economic productivity as people adjust their work and spending habits. Retail, recreation and tourism industries can benefit from extra daylight in evenings.

So in summary, the main goals are energy conservation, safety, aligning daylight to waking hours, and potential economic effects.

How Clocks Shift Forward for the Long DST Check

During the forward, “long” DST check, clocks shift ahead by one hour at a designated time:

  • In most of the U.S. and Canada, clocks move forward at 2:00AM local time on the second Sunday in March.
  • At 1:59:59 AM, clocks jump ahead to 3:00:00 AM.
  • The day “loses” one hour and becomes 23 hours long.
  • Sunrise and sunset will be one hour later compared to standard time.

Here is an example timeline on the day of the DST change in March:

Time Event
1:59 AM Last minute of standard time
3:00 AM Clocks jump forward to 3 AM, DST begins
4:00 AM First hour of DST

To visualize the shift, imagine the missing hour from 2:00AM to 3:00AM is skipped over. So 1:59AM jumps straight to 3:00AM in the transition.

Impact of the Long DST Change on Daylight Hours

Shifting clocks forward by one hour has the effect of moving an hour of daylight from the morning to the evening. Here are some impacts on daylight as a result of the “long” DST check:

  • Sunrise will be approximately one hour later in the morning.
  • Sunset will be about one hour later in the evening.
  • The extra hour of evening daylight saves energy by reducing lighting needs.
  • Morning daylight is reduced, which could affect commuters.
  • Evening daylight supports more outdoor and economic activity.

So in summary, the forward DST change pushes daylight from morning to evening hours to better match waking and working schedules.

Example Daylight Changes

Here is an example of how sunrise and sunset times change with the long DST check in New York City:

Date Sunrise Sunset
March 12 (before DST) 6:20 AM 6:01 PM
March 13 (after DST) 7:19 AM 7:02 PM

As shown, sunrise and sunset are pushed approximately one hour later after the “spring forward” DST change.

Effects of the Long DST Change on Sleep and Health

Shifting clocks forward by one hour can temporarily disrupt sleep cycles and health for some people. Here are some potential effects:

Lost Hour of Sleep

The day is shortened by one hour, which means one less hour to sleep if bedtimes remain the same.

Sleep Disruption

Losing an hour can disrupt sleep rhythms and quality. This may make people groggy and tired the next day.

Increased Heart Attack Risk

Studies show a small increase in heart attack risk in the days after the DST time shift.

Accident Risk

Higher accident risk can result from fatigue and lost focus after the DST change.

Mood Disorders

Some individuals, particularly those prone to depression, may experience worse mood after the DST shift.

Most effects are minor and temporary as people adjust. But those with existing health conditions should take extra care.

Tips for Coping with the Long DST Change

It takes most people several days to adjust their sleep patterns and energy levels after the hour shift forward in spring. Here are some tips that can help cope with the DST change:

  • Gradually adjust bedtimes in the days leading up to the time change.
  • Set alarms to wake up earlier and re-align your body clock.
  • Expose yourself to morning sunlight to help reset circadian rhythms.
  • Be extra careful when driving due to fatigue and drowsiness.
  • Avoid scheduling important events for the Monday after the change.
  • Stay hydrated and limit alcohol to avoid worsening sleep loss effects.

The body typically adapts within one to two weeks. Remaining patient, allowing extra rest, and maintaining healthy habits can ease the adjustment.

Differences From the Short DST Check in Fall

The clock change process is reversed in the fall with the “short” DST check. Here are the key differences compared to the spring “long” check:

  • Happens in early November instead of March.
  • Clocks shift back one hour instead of ahead.
  • Gains an extra hour instead of losing one.
  • Sunrise and sunset are shifted one hour earlier.
  • Can disrupt sleep but most people adjust quicker.

This fall time change causes an extra hour of sleep, more morning daylight, and earlier evening sunsets. The effects tend to be less disruptive for most people compared to the spring.

Controversies and Problems with DST and Clock Shifts

Despite the intended benefits, DST has also long been controversial. Here are some key issues with biannual clock shifts:

Disrupted Circadian Rhythms

Evidence shows DST disturbs normal circadian biology for humans, animals and plants. This can have negative health effects.

Accident Risks

Contrary to the expected safety benefits, studies show accident risk increases right after the DST changes, due to sleep loss.

Reduced Productivity

The fatigue and attention loss around both DST changes lowers work and school performance and productivity.

Harms Tourism Industry

Frequent time changes can reduce tourism activity. Coordination between neighboring regions is also disrupted.

Does Not Save Energy

Modern studies show minimal or no energy savings from DST. Artificial lighting use has decreased while heating and AC use has increased.

Efforts to Abolish Seasonal Time Changes

Due to increasing dissatisfaction, several regions have abolished DST and stick to standard time year-round. For example:

  • Russia eliminated seasonal time changes in 2011 after a public poll.
  • The European parliament voted in 2019 to end the practice, but implementation stalled.
  • Some U.S. states, like Florida and California, have proposed keeping standard time.

However, ending DST can be complicated globally due to economic integration and transportation coordination between neighboring countries and states.

Permanent Daylight Saving Time vs. Standard Time

If seasonal clock shifts are abolished, there is debate over using permanent DST or permanent standard time instead. Here is some comparison:

Permanent Standard Time Permanent Daylight Time
Morning Light More Less
Evening Light Less More
Energy Use Lower Higher
Sleep Cycles More stable More disrupted

Research indicates permanent standard time may be better aligned with human circadian biology. But there are arguments on both sides of the issue.


  • The long DST check shifts clocks forward one hour in spring, usually early March in the U.S.
  • It aims to provide more usable daylight during waking hours and conserve energy.
  • The time change can temporarily disrupt sleep cycles and increase accident risks.
  • Gradual adjustment and healthy habits can ease the transition.
  • There is ongoing debate about abolishing seasonal time shifts entirely.

In summary, the forward DST change provides extra evening daylight but comes with short-term disruption. Whether the benefits outweigh the costs remains controversial. But the biannual clock shifts are likely to continue in most regions for the foreseeable future as changing established conventions is difficult.