Countdown Timer
Runs locallyInput stays in your browserFree, no sign-up
A countdown is simple arithmetic — target timestamp minus now, converted into days, hours, minutes and seconds. But simple is not the same as convenient: the timer on your phone is built for minutes and hours, not for “87 days and 14 hours from now”, and search-engine countdown widgets need a network connection. This tool stores your target as a millisecond timestamp and recomputes “target minus now” from scratch every second. Because each refresh is a full recalculation rather than an accumulation, the display never drifts — even if the browser throttles a background tab, it snaps back to the correct value the moment you return, accurate to the second. Everything runs locally in your browser, so it works offline too.
Three everyday uses. First, exams and deadlines: set the date of an exam, a certification test or a project delivery, and check the remaining days each morning — far more reliable than mental math, and handy for planning backwards from the date. Second, things to look forward to: a wedding, a trip, a baby's 100th day, concert tickets going on sale. Give the countdown a name and it becomes something you can share, which makes the wait more fun. Third, short reminders: use the quick buttons for “in 1 hour” or “in 3 hours” when the oven is on or a meeting is about to start — when time is up the page shows a clear message and plays an alert sound.
A few things to know. The target must be in the future — picking a past time shows a prompt to choose again. The date-time picker is interpreted in your browser's local timezone, and because the target is stored as an absolute timestamp, the remaining time stays correct even if you travel across timezones. The countdown needs the page to stay open: closing the tab stops the timer and the alert sound will not play. Your data is not lost, though — the target is saved automatically in the browser, and reopening the page resumes the countdown as long as the time has not passed yet. On precision: the display is accurate to the second; different browsers throttle background tabs differently, but the number re-syncs itself when you come back.
On privacy: your target date and event name live only in this device's browser storage. Nothing is uploaded to any server, no account is needed, and the “Clear” button wipes everything. On a shared computer, remember to clear it when you are done.
How to use
- Pick the target date and time under “Target date & time”, and optionally name the event.
- Use a quick button for 1 hour, tomorrow or 7 days out — or pick a date manually and press “Start countdown”.
- Watch the remaining days and HH:MM:SS tick every second; when time is up the page shows an alert and plays a sound.
FAQ
Is the countdown accurate? Does it drift in a background tab?
It is accurate to the second and never drifts. Every refresh recomputes target-minus-now from scratch instead of accumulating, so even when the browser throttles a background tab, the display re-syncs to the correct value the moment you return.
Does it keep running after I close the page?
No — closing the tab stops the JavaScript and the timer with it, so no sound will play. But your target is saved automatically in the browser, and reopening this page resumes the countdown as long as the time has not passed.
What if I change timezones or switch devices?
On the same device, changing timezones is fine: the target is stored as an absolute timestamp, so the remaining time stays correct. On a different device you need to set it again, because the data lives only in the original browser.
What happens when time is up?
The page shows a “Time's up!” message and plays three alert tones (you can turn the sound off with the checkbox below the timer). The sound needs the page to stay open and the browser to allow audio; on phones, check the device is not muted.
Is my target date uploaded anywhere?
No. The date and event name stay in your browser's local storage and no network request is ever sent. The “Clear” button deletes them completely.