With the return to solar time we gain an hour in the night, but this does not necessarily mean we feel more rested. Changing schedules and light exposure can affect your sleep-wake rhythm. Here’s what science says.
On the night between Saturday 24th and Sunday 25th October solar time returned. At 3 o’clock the hands were moved back an hour, returning to 2 o’clock. A small gift for those who love to sleep: sixty more minutes available. Yet, in the next few days, some may experience increased tiredness, difficulty falling asleep or a certain drowsiness during the afternoon.
It is not necessarily a contradiction: our body does not regulate sleep only by counting the hours spent in bed, but also follows an internal biological clock, influenced above all by the alternation between light and darkness.
The transition to solar time suddenly changes the relationship between the times of our activities and natural light. Although the fall change is generally less problematic than the spring change, some people may need a few days to adjust.
Because an extra hour of sleep doesn’t necessarily mean more rest
The person responsible is the circadian rhythm, the system that regulates numerous body functions over the course of approximately 24 hours, including sleep, wakefulness, body temperature and the secretion of some hormones.
This internal clock is synchronized primarily by light. Exposure to natural light in the morning promotes the state of wakefulness and helps regulate sleep times, while darkness in the evening facilitates the body’s preparation for rest.
With the return to standard time, the Sun rises and sets about an hour earlier according to the clock. Our biological rhythm, however, does not change instantly along with the hands.
As a result, those who used to fall asleep and wake up at certain times may temporarily experience a phase shift. For example, you may feel sleepy earlier than usual in the evening or wake up spontaneously too early in the morning.
According to the American Academy of Sleep Medicine (AASM), misalignment between body clock, sunlight, and social schedules is one reason seasonal time changes can interfere with rest.
The problem is not only sleep, but also light
There is another aspect to consider: from today it will get dark earlier. Going back to standard time doesn’t actually shorten the days by an hour. The duration of natural light continues to gradually decrease as winter approaches. However, what changes abruptly is its distribution with respect to the times we use every day.
We will have more light in the early morning hours, but less in the late afternoon, just when many people leave work or school.
Natural light represents one of the main signals that regulate our biological clock. For this reason, spending most of the day indoors and receiving little light outdoors can make it more difficult to maintain a regular sleep-wake rhythm.
The US Centers for Disease Control and Prevention (CDC) points out that exposure to light at different times of the day can change circadian rhythms and affect the quality of sleep.
However, a distinction must be made: returning to solar time is not in itself harmful to the body. Indeed, standard time generally guarantees a better correspondence between morning light and the biological clock than summer time.
The time change in autumn is less problematic than the spring one
The consequences of the two seasonal changes are not identical. When daylight saving time comes into effect in March, we lose an hour and have to move forward. It is a condition that can reduce the time available for sleep and which, according to several studies, is associated with a temporary increase in some health and safety risks.
In October, however, the hands are moved back, this step is generally easier to manage, because it allows you to postpone the times compared to the previous reference.
It doesn’t mean that everyone immediately benefits. People with very regular sleep schedules, shift workers, or those who already suffer from sleep disorders may still feel some changes.
It is important, however, not to automatically attribute symptoms such as persistent tiredness, insomnia or difficulty concentrating to solar time. They can have numerous causes, and scientific evidence of the negative effects of the autumn transition is less consistent than that relating to the spring transition.
How to get used to the new time without worsening your sleep
No special remedies are needed, for most people, the body adapts spontaneously to the change. However, some behaviors can promote a smoother transition.
The first is to maintain fairly constant times for going to sleep and waking up, avoiding making up for an unrestful night with long afternoon naps.
It can also be useful to expose yourself to natural light in the morning, for example by walking outdoors or taking advantage of the break before starting work. In fact, morning light helps synchronize the biological clock.
In the evening, however, it is preferable to limit exposure to very intense lights and maintain a regular routine. Avoiding caffeine in the hours before bed can also help, especially for those who are sensitive to its effects.
If fatigue continues for weeks or interferes with normal daily activities, it should not be dismissed as simply a consequence of the time change.
What if we kept standard time year-round?
The debate on the abolition of the seasonal time change has been open for some time. And on the level of sleep health, the position of an important part of the scientific community is quite clear.
In a document published in 2024 in the Journal of Clinical Sleep Medicine, the American Academy of Sleep Medicine expressed its opinion in favor of the permanent adoption of standard time, i.e. solar time, considering it more consistent with human circadian physiology.
The reason mainly concerns the availability of light in the morning, which is fundamental for synchronizing biological rhythms. Maintaining daylight saving time all year would instead mean having later sunrises during the winter.
The point, therefore, is not that solar time makes you sleep worse. Rather, it is the sudden change in timetables that can cause some temporary discomfort.
And that hour gained tonight, however welcome, does not automatically guarantee better sleep: what also counts is how much we usually sleep, the regularity of rest and the relationship between our daily rhythms and natural light.
