Countdown timer
Set a future date and time. Days, hours, minutes, and seconds come from the difference between now and that instant.
Set a target, then start. Remaining time is computed from timestamps, not by subtracting one each second.
How it works
When you press Start, the page converts your wall time in the selected IANA zone into a UTC millisecond timestamp. The display is that timestamp minus the current clock.
How to use it
Choose date, time, and zone. Use presets to add 15 minutes, an hour, a day, or a week from now. Pause freezes remaining duration; restart rebuilds the original target from the form.
Considerations
If the zone observes daylight saving, a wall time in the spring gap may map to the next valid instant. Past targets are rejected with an expired state.
Questions
How accurate is the countdown?
Each tick computes target timestamp minus Date.now(). Background throttling can delay a paint, but the value snaps back when the tab is visible again.
Can I share a countdown?
Yes. Copy link stores date, time, and time zone in the query string.
What happens at zero?
The display stays at zero. Optional sound uses the Web Audio API. Notifications require permission.
Related tools
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How Long Until
See days, hours, minutes, and seconds remaining until a clock time or date.
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Days Until
Count the days, weeks, and months remaining until a target date.
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Event Countdowns
Live countdowns to recurring holidays and notable dates.
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Online Timer
Set hours, minutes, and seconds. The remaining time is tracked from timestamps.