Countdown Timer
Countdown Timer — runs in your browser. Inputs are not stored.
Countdown timer
Enter values, then press Calculate.
Counts down to the target date and time in real time, to the second. Values stay in your browser only.
How to use
- Pick date and time in Target datetime. Input follows the browser’s local calendar format.
- Press Start so status becomes running and time remaining ticks down by the second.
- Press Pause to stop. Status becomes paused and the numbers stay.
- Press Start again to recount remaining time to the same target from now. Time that passed while paused is included.
- Reset sets remaining time to --:--:-- and status to idle. The target datetime field can stay.
- An empty target shows a prompt to enter a target datetime; a broken format shows an invalid datetime message.
Key concepts
A countdown timer shows target time minus now. This screen uses the device Date clock, not a server clock, so a wrong laptop time skews remaining time. For official opening or exam start, also check the organizer’s clock. The display redraws about every 0.25 seconds and does not guarantee broadcast-grade frame accuracy.
When more than a day remains, a day count prefixes hours:minutes:seconds. At the target it stops at 00:00:00 and Complete and does not go negative. Inputs and running state stay in the tab and are not sent to a server. Refreshing drops a running count, so you must press Start again. Background tabs may be throttled so seconds can lag. For important deadlines, set the device clock first and keep the screen in front if you can.
Example
Put 8:40 on exam morning in target datetime and days, hours, minutes, and seconds until then shrink in large type. When status is Complete, match it with the exam-room clock. For a short 4-minute noodle timer, a minutes-and-seconds timer alarm fits better. For date-only D−n, the D-day calculator is simpler. If the event is tomorrow, pick tomorrow’s time; if the time already passed, it Completes as soon as you Start.
Related: timer alarm · D-day calculator · count-up timer
Frequently asked questions
Does the countdown timer use Korea Standard Time?
No. It is the device local time the browser reads. Setting the time zone to Seoul is close to KST.
Is countdown-timer input saved?
It is not saved or sent. Closing or refreshing the page also drops a running count.
Can I countdown an event several days away?
Yes. Past one day, a day count prefixes hours:minutes:seconds.
What happens when the target time has passed?
Remaining time is 00:00:00 and status is Complete. It does not keep counting negative.
If I pause the countdown then start again, does it restart from scratch?
If the same target datetime remains, remaining time until then is counted again. If that time already passed, it Completes immediately.
How does a timer alarm differ from a countdown timer?
A timer alarm takes minutes and seconds and can beep at the end. This screen shows time left until a specific date and time and has no sound.
Last reviewed: 2026-09-04