The clock change and your sleep
Short answer: the spring transition is the one that matters. Losing an hour is a genuine, measurable disruption — fatal crashes rise about 6% in the week after it — and the fix is to move your schedule gradually over the preceding few days rather than absorbing the whole hour at once. The autumn transition is mostly harmless and mostly self-correcting.
The two transitions are not equivalent
They get discussed as a pair, but they do different things to you.
Spring forward takes an hour of sleep away and shifts your required wake time earlier relative to your body clock. If you normally get up at 6:30, you're now getting up at what your body still experiences as 5:30. This is the harder direction for the human circadian system in general — advancing (going earlier) is consistently harder than delaying.
Fall back gives an hour back and shifts your wake time later relative to your body clock. Most people find this easy. The usual complaint is waking early for a few days and losing evening daylight, which is a mood and lifestyle issue rather than a sleep-mechanics one.
The evidence on spring forward
A study published in Current Biology analysed 732,835 fatal crashes in the US between 1996 and 2017 and found a roughly 6% increase in fatal crashes during the workweek following the spring transition — around 28 additional deaths a year. In the western parts of time zones, where the sun rises later relative to clock time, the increase exceeded 8%.
Two details make that finding harder to dismiss as coincidence. First, the effect wasn't there in autumn: morning and evening crash patterns shifted in opposite directions and cancelled out, with no net change. Second, when the US moved the spring transition from April to March in 2007, the crash spike moved with it.
Cardiovascular effects have also been reported around the spring transition, though the literature there is more mixed and the individual risk increase is small. The crash data is the cleaner signal, and the mechanism behind both is the same: a population that is collectively an hour short of sleep and internally misaligned for several days.
2026 and 2027 dates
| Spring forward | Fall back | |
|---|---|---|
| UK / EU 2026 | 29 March | 25 October |
| US / Canada 2026 | 8 March | 1 November |
| UK / EU 2027 | 28 March | 31 October |
| US / Canada 2027 | 14 March | 7 November |
The US uses the second Sunday of March and the first Sunday of November. The UK and EU use the last Sunday of March and the last Sunday of October. This means there are a few weeks each year when the usual transatlantic time difference is an hour off from what people expect — worth knowing if you take early calls across the Atlantic, or set alarms for them.
Arizona (excluding the Navajo Nation), Hawaii, and most of Saskatchewan don't observe it at all.
The plan for spring forward
The whole idea is to arrive at the transition already partly adjusted, so you're absorbing 15–20 minutes rather than 60.
Starting four days out: move bedtime and wake time 15 minutes earlier each day. By Saturday night you're 45–60 minutes ahead and Sunday costs you almost nothing.
Prioritise the wake time. Wake time is the stronger anchor for your body clock than bedtime. Setting an alarm 15 minutes earlier reliably works; deciding to fall asleep 15 minutes earlier often doesn't. Move the wake time and let bedtime follow as sleep pressure builds.
Get outside early on the Sunday and Monday. Morning light is the main signal that advances your clock. Fifteen to thirty minutes of daylight soon after waking does more than anything else on this list. Through a window is weaker but not useless; outdoors is much better, even on an overcast day.
Dim things down in the evening. Bright light late pushes your clock the wrong way, directly opposing what you're trying to do. The two or three evenings around the transition are the ones worth being deliberate about.
Skip the Sunday afternoon nap. It's tempting when you're short an hour, and it will make Sunday night harder, which is the night that actually matters. If you must, keep it under 30 minutes and before mid-afternoon.
Be careful driving on Monday. Given the data, this is the one piece of advice with a body count attached. Leave extra time, and treat the Monday commute as though you're more impaired than you feel — because collectively, people are.
The plan for fall back
Much shorter, because much less is needed.
The extra hour is real but most people squander it by staying up late, which reproduces the sleep debt they were just handed a chance to clear. Going to bed at your normal clock time on the Saturday and taking the hour as extra sleep is the better use of it.
The genuine difficulty in autumn isn't the hour — it's that sunset suddenly lands in the late afternoon. That shift in evening light exposure affects mood for some people, and if that's a pattern you recognise from previous years, morning light exposure and, for some, discussing seasonal low mood with a doctor are the things that help. A vibrating alarm doesn't solve that one.
Where this intersects with alarms
For four or five days after springing forward, you're being woken earlier than your body has planned for. That's exactly the condition that produces the worst sleep inertia, and it's the week when dismissing your alarm without remembering it is most likely — sleep-dismissing happens when you're woken out of deeper sleep, and you will be.
A few practical adjustments for that week specifically:
- Move your phone out of reach if you're a habitual sleep-dismisser. This is the week it matters most.
- Set a backup alarm on a different device, five to ten minutes after the first.
- Don't rely on waking naturally. Anticipatory waking — surfacing just before your alarm — is trained on your habitual schedule, and the clock change invalidates it for several days.
If your household is on different schedules, this is also the week the earlier riser is most likely to wake everyone else while fumbling for a snooze button in the dark. A silent, wrist-worn alarm like Silent Wake is genuinely useful here for the same reason it is any other week: the vibration reaches you and nobody else, and there's no sound to sleep through or to wake your partner.
On whether any of this should still be happening
Both the American Academy of Sleep Medicine and the Sleep Research Society have argued for abolishing seasonal clock changes in favour of permanent standard time — the position being that standard time is better aligned with solar time and therefore with human circadian biology than permanent daylight saving would be. The EU parliament voted in 2019 to end mandatory changes and it has not been implemented. So for now, the transitions continue, and the practical question is just how to handle them.
Related reading
- Sleep Inertia Explained
- The Case for a Consistent Wake Time (Even on Weekends)
- How to Wake Up on Time in a New Time Zone
- Why You Wake Up Right Before Your Alarm
General information, not medical advice. Transition dates are the published rules for the UK/EU and US/Canada; local exceptions exist. If clock changes reliably trigger something more serious than a few tired days, that's worth raising with a doctor.