Does it drift when the tab is in the background?

No. Browsers do throttle timers in background tabs, but each update here recalculates target minus current time, so the correct remaining time appears the moment you return. Nothing accumulates.

Does the countdown survive closing the tab?

No. The target lives only in browser memory and is never written to the URL or storage, so it disappears when the tab closes. That is a deliberate privacy trade-off: nothing is stored, so no record of what you were counting down to is left behind.

DATE AND TIME · CALCULATED IN YOUR BROWSER

Countdown Timer

Count down to a target time and stay accurate through background tabs and sleep.

Target time

Date

Time

The target lives only in browser memory and disappears when the tab closes.

About this tool

Set a target date and time and the timer counts down in days, hours, minutes, and seconds. Each update recomputes target minus now rather than decrementing a running total, so switching to another tab, letting the device sleep, or even changing the system clock leaves the number correct when you come back. Once the target passes, it switches to showing how long ago it was.

How it works

Set the target date and time.
Start the countdown; pause or reset at any point.
Switch tabs and come back — the number is still right.

Assumptions

Every tick is recalculated from the target time so error cannot accumulate. The target only lives in browser memory.

Privacy

Every calculation runs inside this browser. Dates and birthdays are never uploaded, stored, or written to the URL or any log.

Frequently asked questions

Does it drift when the tab is in the background?: No. Browsers do throttle timers in background tabs, but each update here recalculates target minus current time, so the correct remaining time appears the moment you return. Nothing accumulates.
Does the countdown survive closing the tab?: No. The target lives only in browser memory and is never written to the URL or storage, so it disappears when the tab closes. That is a deliberate privacy trade-off: nothing is stored, so no record of what you were counting down to is left behind.

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