Set the alarm clock for 3:51 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 3:49 am Alarm clock for 3:50 am Alarm clock for 3:52 am Alarm clock for 3:53 am

Going to bed for a 3:51 am alarm

Asleep by 6:36 pm — 6 full sleep cycles, about 9 hours
Asleep by 8:06 pm — 5 full sleep cycles, about 7 hours
Asleep by 9:36 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.

3:51 am across the country

Sydney	3:51 am
Brisbane	3:51 am
Adelaide	3:21 am
Perth	1:51 am
Darwin	3:21 am

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

How to use the online alarm clock

An alarm at 3:51 am in the dead of night usually means a red-eye flight, a delivery run, or a newborn's next feed. This sets a browser alarm for 3:51 am that rings through your laptop speakers, so you don't need to fumble for your phone in the dark. Leave the tab open and it'll do the waking for you.

Choose a sound before you press Start — something like a chime or a classic bell tends to work better than anything too gentle. Once it's running, the countdown happens right here in the browser, which means the tab needs to stay open in the background rather than being closed.

Because this runs in the browser rather than on the phone's operating system, it sidesteps silent mode and do-not-disturb entirely, useful if your phone alarm has ever failed to go off for exactly that reason. Just be aware it needs the tab open and the screen or laptop lid to stay on to actually ring. On a 24-hour clock 3:51 am is written 03:51, and spoken aloud it's nine minutes to four at night. You'll also see it written 3.51 am — a full stop instead of the colon means the same time. If you need it loud, turn the system volume up before you start: the alarm plays at whatever the device is set to.

Common questions

Is this alarm accurate across daylight saving time?

It uses your device's local clock, so as long as your computer's time and date settings are correct, it'll adjust automatically when daylight saving time starts or ends.

Can I use this on my phone instead of a laptop?

Yes, it works in a mobile browser the same way, but phones are more likely to lock the screen or sleep, which can stop the alarm from ringing. A laptop or desktop tends to be more reliable for this.

Can I set more than one alarm at a time?

This page is built around a single alarm at a time. For multiple alarms, open a separate tab for each one and set a different time in each, keeping every tab open until it's rung.

Why use a browser alarm instead of my phone's built-in one?

Mainly for reliability against silent mode, do-not-disturb, or a phone left charging out of earshot. It's a useful backup or a desk-based alternative, though it depends on this tab staying open rather than running in the background of your phone.