Set the alarm clock for 4:21 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 4:19 am Alarm clock for 4:20 am Alarm clock for 4:22 am Alarm clock for 4:23 am

Going to bed for a 4:21 am alarm

Asleep by 7:06 pm — 6 full sleep cycles, about 9 hours
Asleep by 8:36 pm — 5 full sleep cycles, about 7 hours
Asleep by 10:06 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.

4:21 am across the country

Sydney	4:21 am
Brisbane	4:21 am
Adelaide	3:51 am
Perth	2:21 am
Darwin	3:51 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 for 4:21 am is usually about catching something before the rest of the world is awake: a ferry, a flight, or a change of shift. Set the time, pick a tone, and leave this tab open. At 4:21 am it'll ring through your device's speakers until you tell it to stop.

Pick whichever sound you're most likely to actually notice, then press Start. The alarm is tied to this browser tab, so it needs to stay open. Minimising the window is fine, but closing the tab or the browser will stop the countdown before it ever rings.

Unlike a phone alarm, this one won't ring if you close the tab, put the computer to sleep, or shut the lid, so it suits a desk, a kitchen bench, or anywhere the device stays powered on and awake. It's free to use and doesn't need an account, but it's not built for unattended overnight use. On a 24-hour clock 4:21 am is written 04:21, and spoken aloud it's twenty-one minutes past four at night. Timetables and rosters may show it as 04:21, and handwritten notes as 4.21 am. Whether you would say set alarm for 4:21 am or put an alarm on for 4:21 am, the steps are the same: pick a sound, press Start, leave the tab open.

Common questions

Do I need to create an account or download anything?

No, there's nothing to sign up for and nothing to install. Pick a time and a sound, press Start, and it runs entirely in this browser tab.

Can I change the alarm sound?

Yes, there's a short list of tones to choose from before you press Start. Pick whichever one you're most likely to actually hear — softer sounds are easier to sleep through than a firm chime or bell.

What happens once the alarm goes off?

It rings through your device's speakers on a loop until you stop it from this page. There's no separate app notification, so make sure your volume is turned up before you rely on it.

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.