Set the alarm clock for 4:37 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 4:35 am Alarm clock for 4:36 am Alarm clock for 4:38 am Alarm clock for 4:39 am

Going to bed for a 4:37 am alarm

Asleep by 7:22 pm — 6 full sleep cycles, about 9 hours
Asleep by 8:52 pm — 5 full sleep cycles, about 7 hours
Asleep by 10:22 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.

4:37 am across the country

London	4:37 am
Birmingham	4:37 am
Manchester	4:37 am
Glasgow	4:37 am
Belfast	4:37 am

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

How to use the online alarm clock

Preparing early to take over a shift in the Underground control room gives you time to set a 4:37 am alarm before it is needed. That leaves a useful margin for checking your pass, notes and route before the 5:00 am handover. Keep the alarm active and the computer awake, because otherwise it will not sound and your shift preparation could run late.

A control room may be quiet while the night service winds down, or busy with radio traffic and handover conversations, so choose the alarm tone for the setting. A softer sound can be enough beside you in a calm room without startling colleagues. If you may be away from the desk or wearing an earpiece, use a more persistent tone and set the volume high enough to stand apart from operational sounds. Test it briefly while you are still preparing.

Before dawn, background noise can change quickly as cleaners finish, staff arrive and early services begin moving through the network. Place the alarm close enough to hear at 4:37 am, but away from radios or panels that may mask it. If the room is currently silent, allow for the extra activity likely nearer 5:00 am when deciding the volume.

Common questions

Does the alarm still work if I close the tab?

No. Everything runs inside this page, so closing the tab — or quitting the browser altogether — ends the countdown there and then. Leaving it open in the background is all it asks, and switching to another tab makes no difference.

What happens if my laptop goes to sleep before 4:37 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.