Do alarms change with daylight saving time? Yes — with two exceptions

Yes. Your iPhone alarm follows the clock, not the hour. Set it for 7:00 AM and it fires at 7:00 AM on the new time — you don't need to change anything, and you shouldn't try to "compensate" by moving it an hour.

There are exactly two ways that goes wrong, and one much bigger problem that has nothing to do with your phone.

When the clocks change: in the UK and EU they go back on Sunday 25 October 2026; in the US and Canada on Sunday 1 November 2026, at 2:00 AM local time, when the clock falls back to 1:00 AM. The two regions are a week apart this year.

Quick answer: alarms adjust automatically as long as Settings → General → Date & Time → Set Automatically is on. Don't move your alarm an hour — that's how people end up an hour out. The only genuinely odd case is an alarm set inside the repeated hour. And the week after the change is when alarms actually get slept through.

Why it works automatically

An iPhone alarm is stored as a local clock time, not as a fixed moment in time. It doesn't know or care that 7:00 AM this Sunday is an hour later in absolute terms than 7:00 AM on Saturday. When the system clock rolls back, every alarm simply keeps pointing at the same numbers on the face.

Which is why the classic mistake is over-correcting. Move a 7:00 alarm to 6:00 "to be safe" and you will genuinely wake at 6:00 — the phone already handled it.

Exception 1: automatic time is switched off

The adjustment depends on your phone knowing the time changed. Two settings control that:

1. Settings → General → Date & Time → Set Automatically — on.
2. Settings → Privacy & Security → Location Services → System Services → Setting Time Zone — on.

If someone set the time manually at some point — a common fix after travelling — the phone will sit on the old offset and every alarm will be an hour out. Check this the evening before the change, not the morning after.

Exception 2: an alarm inside the repeated hour

In autumn, the hour from 1:00 to 1:59 AM happens twice. An alarm set in that window is ambiguous, and depending on the device and the year it may fire twice or behave unpredictably. In spring, the same window is skipped entirely, so an alarm set there may not fire at all.

Almost nobody sets a 1:30 AM alarm, so this is mostly trivia — but if you work nights or have a medication alarm in that window, move it outside 1:00–3:00 AM for that one night.

The 30-second check before the clocks change

1. Set Automatically is on.
2. Your alarms are set to the times you actually want — unchanged.
3. Nothing is scheduled between 1:00 and 3:00 AM that night.
4. While you're there: volume up, sound not None, and the rest of the settings that decide whether an alarm is audible at all.

That's it. Go to bed.

The real problem: the week after

Here's the part worth more than everything above. Your phone adjusts instantly. Your body takes days.

Falling back gives you an extra hour that Sunday, which sounds like a gift — and it is, once. But your circadian rhythm is still running on the old schedule, so for several days you'll feel sleepy earlier and wake earlier than the clock says you should. Research on the transitions consistently finds it takes many people the better part of a week to resettle, and the evening darkness arriving an hour sooner doesn't help.

For an alarm, that means something specific: for about a week, your alarm lands at a different point in your sleep cycle than it usually does. The same 7:00 AM that normally catches you in light sleep can now catch you mid-deep-sleep — and an alarm landing in deep sleep is the one you sleep through, or turn off with no memory of doing it.

This is why the Monday after a clock change is such a reliable disaster for heavy sleepers, and why "but my alarm is set correctly" is beside the point.

What actually helps that week

• Morning light, immediately. It's the strongest signal for resetting your body clock — faster than caffeine. Outside within an hour of waking if you can, brightest lamp you own if you can't.
• Shift gradually if you plan ahead. Moving your bedtime 15 minutes for a few nights before the change spreads the adjustment out instead of taking it in one hit.
• Hold your wake time. Don't "use" the extra hour by sleeping in on Sunday — that undoes most of the benefit and makes Monday worse. The sleep calculator works out the bedtime that fits your fixed wake time.
• Don't add more alarms. A wall of backup alarms trains you to ignore the first one, which is the opposite of what a disrupted week needs. If you're reaching for backups because the main alarm keeps failing, compare the best alarm apps for heavy sleepers instead.

And for the mornings when it still fails

If the clock change is the week you historically oversleep, the fix isn't a louder alarm or an earlier one — it's an alarm your half-asleep self can't switch off. WakeUpBroo has no snooze and no dismiss button: it stops only when you type a rotating code shown on wakeupbroo.com/code, which you open on a laptop or another device across the room. Whatever the clocks are doing, the alarm ends with you standing up — which is the only part of this the time change can't affect.