Set the alarm clock for 4:12 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 4:10 am Alarm clock for 4:11 am Alarm clock for 4:13 am Alarm clock for 4:14 am

Going to bed for a 4:12 am alarm

Asleep by 6:57 pm — 6 full sleep cycles, about 9 hours
Asleep by 8:27 pm — 5 full sleep cycles, about 7 hours
Asleep by 9:57 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.

4:12 am across the country

London	4:12 am
Birmingham	4:12 am
Manchester	4:12 am
Glasgow	4:12 am
Belfast	4:12 am

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

How to use the online alarm clock

While preparing your kit for night roadworks on the M25, set the alarm for 4:12 am before you need to leave. That gives you a clear point for putting on your workwear, checking any last travel information and heading out ahead of 5:00 am, without repeatedly watching the clock.

Your M25 roadworks wake-up depends on the browser remaining open and the phone or computer staying awake: if the browser is closed or the device sleeps, the alarm will not sound. Keep this page available, leave the device connected to power if needed and set its volume before turning your attention back to your preparations. A separate phone alarm is sensible if missing the departure would affect the shift.

Before going outside for the overnight shift, allow for the damp feel that often comes with cool air at this hour. Humidity can leave a jacket, gloves or tools feeling clammy even when there is no obvious rain, so keep a dry outer layer within reach and protect anything that should stay dry. At 4:12 am, a brief check beside the door is easier than discovering unsuitable clothing after reaching the motorway.

Common questions

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.

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 4:12 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.