Why Our Bodies Prefer Winter Time

Twice a year, clocks in Spain are moved forward or back as part of the seasonal daylight saving time system, and sleep medicine specialist Miguel Ángel Saiz has offered an explanation for why the body tends to adjust more easily to the autumn change.

Speaking about the shift to winter time, Saiz noted that the human sleep-wake cycle naturally runs on a cycle of approximately 24.6 hours, slightly longer than the standard 24-hour day.

This subtle biological difference, he suggested, may explain why the autumn clock change, which provides an additional hour, tends to be less disruptive than the spring transition, which removes an hour.

Because the body's internal rhythm is already slightly longer than a full day, adjusting to a longer day in autumn aligns more naturally with our biological clock than adapting to a shorter one in spring.

However, Saiz was careful to clarify a common misconception: having an extra 60 minutes does not necessarily translate into additional sleep.

"Contar con 60 minutos adicionales no implica dormir más," he said, pointing out that simply gaining time does not guarantee that people will use it to rest.

The specialist's remarks come amid a broader conversation in Spain and across Europe about the value and effects of the twice-yearly clock change, a practice that has been in place for decades as a way to make more efficient use of daylight through the seasons.

While the biological explanation offered by Saiz helps clarify why many people report feeling less tired after the autumn switch compared with the spring one, it also highlights that the relationship between clock changes and actual sleep quality is more complex than commonly assumed.

Circadian rhythms, the internal processes that regulate the sleep-wake cycle over roughly a 24-hour period, are influenced by multiple factors, including light exposure, daily habits and individual biology, meaning that the effects of time changes can vary significantly between individuals.

Saiz's comments provide a scientific lens through which to understand a seasonal ritual experienced by millions of people each year, even as debate continues over whether such changes remain necessary or beneficial in modern society.

For now, the twice-yearly adjustment remains in place in Spain, with the specialist's insights serving as a reminder that the body's relationship with time is rarely as simple as moving a clock hand.