Set the alarm clock for 5:24 am

Leave this tab open — the alarm only rings while the tab stays open.

The alarm goes off in: ::

You can also try the other alarm clocks

Alarm clock for 5:22 am Alarm clock for 5:23 am Alarm clock for 5:25 am Alarm clock for 5:26 am

Going to bed for a 5:24 am alarm

Asleep by 8:09 pm — 6 full sleep cycles, about 9 hours
Asleep by 9:39 pm — 5 full sleep cycles, about 7 hours
Asleep by 11:09 pm — 4 full sleep cycles, about 6 hours

A sleep cycle runs about 90 minutes, and most people take around 15 minutes to drop off. Waking at the end of a cycle feels easier than waking in the middle of one.

5:24 am across the country

London	5:24 am
Birmingham	5:24 am
Manchester	5:24 am
Glasgow	5:24 am
Belfast	5:24 am

Times are worked out live in your browser, so daylight saving is already accounted for.

How to use the online alarm clock

Pause your packing or last-minute document check at 5:24 am and let the alarm mark the moment to leave for Heathrow security. It gives you a clear break from whatever has absorbed your attention, whether that is finding a passport or fastening a suitcase. With 6:00 am approaching, the signal can separate home preparations from the next stage of your early flight.

Your Heathrow preparations may continue in another app, so keep this page active and the sound turned up while the alarm is set. If this browser page is closed or your phone goes to sleep, the alarm will not sound to pull you back to your flight preparations. Check the displayed alarm time before returning to your task, and use a separate alarm on your phone if missing the cue could delay your journey.

The short move from a taxi, coach or car park into the terminal may feel different from the warm indoor air you have just left. At this early hour, check the local conditions before setting off: damp air can make luggage handles and outdoor surfaces feel clammy. Keep a light layer within reach rather than buried in your case, especially if you expect to wait outside before entering Heathrow.

Common questions

What happens if my laptop goes to sleep before 5:24 am?

The tab sleeps along with it and the alarm will not sound on time, if at all. If you are relying on it, change the power settings so the machine stays awake, or keep a phone alarm running as well.

Do I need an account or an app?

Neither. Choose a time and a sound, press Start, and it runs in this browser tab. Nothing is downloaded, nothing is registered, and closing the page leaves nothing behind on the device.

Can I change the sound?

Yes, there is a short list of tones to pick from before you press Start. Softer sounds are easy to sleep through, so a firmer bell tends to be the safer choice for anything early in the morning.

Will it still be right when the clocks change?

Yes. It reads your device's local clock, so the move between GMT and BST at the end of March and October is picked up automatically, as long as the computer's date, time and time zone are set correctly.