Set the alarm clock for 4:52 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 4:50 am Alarm clock for 4:51 am Alarm clock for 4:53 am Alarm clock for 4:54 am

Going to bed for a 4:52 am alarm

Asleep by 7:37 pm — 6 full sleep cycles, about 9 hours
Asleep by 9:07 pm — 5 full sleep cycles, about 7 hours
Asleep by 10:37 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.

4:52 am across the country

London	4:52 am
Birmingham	4:52 am
Manchester	4:52 am
Glasgow	4:52 am
Belfast	4:52 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 open the Royal Mail sorting centre means having the 4:52 am alarm ready before the shift depends on it. That leaves a brief margin before 5:00 am for getting dressed, checking keys and gathering anything needed for the journey. With those details settled beforehand, the alarm marks a clear point to move rather than the start of a hurried search in the dark.

For a Royal Mail sorting centre opening, the main risk is leaving the alarm on equipment that enters sleep mode before 4:52 am. The selected time and sound can be checked while preparing, with the browser kept active and the equipment connected to power if necessary. This browser alarm will not sound after its session has been closed or the equipment has fallen asleep, so the sorting centre opening could be missed. A separate alarm clock or phone alarm provides sensible backup for a shift that cannot wait.

Leaving for the sorting centre during the night can disturb anyone sleeping nearby, especially when clothes, keys or a work bag are gathered after the alarm. Placing those items by the door earlier keeps movement and cupboard noise down at 4:52 am. A moderate alarm volume positioned close to the sleeper is also less likely to wake the rest of the house than a loud tone sounding across the room.

Common questions

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.

Can I use this on a phone?

It works in a mobile browser, but phones lock the screen and suspend background tabs far more readily than a laptop does, which can stop the alarm sounding. For anything important, a desktop or a plugged-in laptop is the steadier option.