The time change: what it does to our body and how to adapt

The clock change is happening again this weekend — in the early hours of Sunday, clocks go back one hour and winter time begins. Despite being a long-standing routine, many people feel the impact of this small adjustment on their body and mood.

Why do we change the clocks?

The idea emerged over a century ago, to make better use of daylight and save energy. However, more recent studies show that those savings are minimal and that the change can affect sleep, wellbeing, and even the risk of accidents in the days that follow.

Today, several countries — such as Spain — want to put an end to the clock change, arguing that the health impact no longer justifies the potential benefits. But what is the actual effect of the time change on us?

What happens to our body

The human body follows an "internal clock" regulated by natural light. When we shift the time, even by just 60 minutes, that balance is disturbed. The result can resemble a mild jet lag: difficulty falling asleep, fatigue, reduced concentration, and changes in appetite.

During the first few nights it is normal to feel greater sleepiness or irritability. Some people adjust in just two days; others may need a week or more. Children, teenagers, and those who already sleep lightly tend to feel the impact even more strongly.

Studies also indicate that, immediately after the change, there is a slight increase in accidents and cardiac events — particularly when an hour of sleep is lost, as happens in March. The winter time shift, on the other hand, tends to affect mood and energy more, as the days grow shorter and darker.

Effects on mood and mental health

Less sunlight and greater sleep disruption can influence our emotional state. It is common to feel more fatigue, apathy, or reduced motivation in the weeks following the change.

Some European studies even point to an increase in depressive episodes after the shift to winter time. The explanation lies in natural light: it regulates the production of melatonin and serotonin, hormones linked to sleep and wellbeing. When darkness falls earlier, the body tends to produce more melatonin and less serotonin, which can affect mood.

Should the clock change be abolished?

Most experts say yes. The Portuguese Sleep Association and other organisations recommend maintaining winter time year-round, as it is more closely aligned with the natural rhythm of light and darkness. Brighter mornings help us wake up, improve concentration, and support healthy sleep patterns.

Permanent summer time, on the other hand, would leave mornings too dark, potentially increasing fatigue and affecting mood throughout the winter.

How to ease the adjustment

While the changes continue, there are simple ways to reduce the impact:

• Adjust your sleep gradually: go to bed and wake up 15 to 30 minutes later (or earlier, as the case may be) in the days leading up to the change.
• Get natural light in the morning: it helps your body reset its biological clock.
• Keep regular routines: stable mealtimes, exercise, and rest schedules make adaptation easier.
• Avoid bright lights and screens before bed: blue light inhibits melatonin production.
• Sleep in a dark, quiet environment: quality sleep is essential for physical and mental balance.

If, even so, you feel that something is not right — if fatigue, irritability, or sadness persist — seek support from a mental health professional. Speaking with a psychologist can help you understand what you are feeling and find your balance again.