Set the alarm clock for 3:55 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 3:53 am Alarm clock for 3:54 am Alarm clock for 3:56 am Alarm clock for 3:57 am

Going to bed for a 3:55 am alarm

Asleep by 6:40 pm — 6 full sleep cycles, about 9 hours
Asleep by 8:10 pm — 5 full sleep cycles, about 7 hours
Asleep by 9:40 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.

3:55 am across the country

London	3:55 am
Birmingham	3:55 am
Manchester	3:55 am
Glasgow	3:55 am
Belfast	3:55 am

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

How to use the online alarm clock

As you finish the shift and prepare to leave, the 3:55 am alarm marks the point for releasing the replacement crew onto the railway tracks. It leaves a short, defined handover before 4:00 am, so access can begin at the agreed hour rather than drifting while everyone waits for confirmation.

For a signal needed during the final handover, an advance check is more useful than discovering a problem at 3:55 am. The alarm can be set briefly beforehand to confirm that the sound is audible and the volume suits the working area, then reset for the actual time. A separate back-up remains necessary because this browser alarm cannot alert the railway crew after its running page has ended or the computer has gone to sleep.

Leaving a night shift can make small sounds seem unusually loud in a quiet house. Before heading home, the alarm volume can be kept only as high as the railway handover requires, with vibration used where available. If the alarm will sound indoors, placing the phone close by reduces the chance of waking other people while still making 3:55 am hard to miss.

Common questions

What happens if my laptop goes to sleep before 3:55 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.