It is 7 a.m., and the alarm rings at its usual time, but the body still feels as if it is in the middle of the night. Three weeks after the switch to winter time on October 25, 2026, millions of French people are still experiencing a diffuse fatigue, a mood that fluctuates like a saw, which should no longer be current. A simple shift of one hour, almost trivial on paper, but apparently continues to cause silent damage. Why does the body take so long to digest this change, and more importantly, how can it be helped to finally turn the page? The circadian clock adjusts to light and not instantaneously, which explains an adaptation that can last several weeks after the time change. This shift weakens sleep, mood, and alertness, with an increased risk of traffic accidents in the late afternoon. The switch to winter time, which took place during the night of October 24 to 25, 2026, provided an additional 60 minutes of sleep, an exceptional night of 25 hours where the clocks went back from 3 a.m. to 2 a.m. A gift in appearance, but not really one for the circadian clock, this internal mechanism that synchronizes body temperature, hormones, and sleep cycles. Unlike a watch, this biological clock does not adjust with a snap of the fingers. It reacts mainly to light, and this change abruptly alters the light cues of the morning and the evening. As a result, the body continues to function according to its old rhythm for several days, or even several weeks for the most sensitive organisms. Sleep, mood, alertness: the triple shock that your body undergoes This shift, however minimal, does not limit itself to a few more yawns in the morning. It affects several areas at the same time. Sleep becomes more fragmented, less restorative, because the morning light, the main signal that tells the brain it is time to wake up, now arrives later. Mood also suffers, with a drop in energy that gradually sets in, especially when the days shorten at the same time. Finally, alertness decreases, and this is not an insignificant detail: rain, dead leaves, and reduced light form a delicate cocktail on autumn roads, making pedestrians and cyclists much harder to spot in the late afternoon. Some studies even mention a link between this disruption of the sleep cycle and increased risks of diabetes, obesity, or cardiovascular disorders, not to mention the increase in fatigue-related accidents. What is striking above all is the speed with which habits shift. Terraces empty earlier, the school dismissal gradually shifts toward darkness, and without realizing it, the entire rhythm of the day contracts. The gentle strategy to help your body finally turn the page Good news, there are simple levers to accompany this transition rather than endure it. The most recommended method is to gradually move the bedtime earlier, about 15 minutes each day, in the days before or after the change. A technique similar to that used by pediatricians to reset children's sleep, and which works just as well for adults. Exposure to natural light also plays a key role: opening the shutters as soon as waking up, or better yet, going out for a walk for a few minutes during the day, helps the brain understand that it is time to get going. Here are some simple reflexes to adopt to limit the effects of this shift: Move bedtime 15 minutes earlier each day before the change, expose yourself to natural light as soon as waking up, avoid bright screens in the evening, maintain regular meal times, and prioritize light physical activity during the day. This famous gain of an hour of sleep can actually reduce part of the accumulated debt and restore a bit of morale, provided the body is given time to regain its bearings. Three weeks, it turns out, is not so long to restore a balance that light, itself, sometimes takes longer to relearn.