The Clock Changed Last Night, But Has Your Body?

As we mentioned in the last article, your body has a clock too. This internal timing system helps regulate when you feel awake and when you feel sleepy. When the clocks suddenly move forward for Daylight Saving Time, we instantly lose an hour on the wall clock, but how long does it take for our body clock to change? Our internal timing system adjusts gradually, which is why many people feel a little tired, foggy, or off during the first few days after the change.

How long does it actually take to adjust?

Research suggests that for most people it takes about three to seven days for the body to fully readjust after losing an hour of sleep in the spring. This happens because the body tends to shift its timing slowly, usually by about 30–60 minutes per day.

The spring change is often harder than the fall change because we are forced to wake up earlier than our body expects, which can temporarily reduce sleep and make mornings feel more difficult.

One simple way to help your body adjust:

One of the most helpful things you can do is get sunlight in the morning. The best option is to step outside for a few minutes after waking up, but even sunlight through a window can help.

Morning light signals to the body that it is time to be awake. The sooner the body receives that signal, the sooner it can begin adjusting to the new schedule.

The clock may change overnight, but the body simply needs a few days to follow.

References:

László et al. (2016): In a review of research on Daylight Saving Time shifts, the authors summarize findings showing that clock changes disrupt sleep and circadian timing and that realignment to the new schedule typically takes up to 5–7 days for most individuals, with some variation between people. 

A review published in Frontiers in Endocrinology explains that when the circadian system is exposed to a shifted light–dark and sleep–wake schedule, without any specific intervention, it only adjusts about 0.5–1.0 hours per day. This gradual shift is what makes adaptations to time changes (like jet lag or the Daylight Saving Time shift) take several days.

A study published in PMC (PubMed Central) found that morning sunlight exposure influences sleep timing and helps align the circadian rhythm. Participants who had more exposure to morning sun showed a significant shift in their sleep midpoint and improved sleep quality, indicating that early light helps the internal clock reset toward an earlier schedule. 

Disclaimer:

 This article is intended for educational purposes only and should not be considered medical advice. Everyone’s body is different, and people adjust to sleep changes at different rates. If you have ongoing sleep problems or health concerns, it is best to speak with a qualified healthcare professional.