Compute time remaining until any target date.
Countdown Calculator does its work in front of you rather than sending anything away to be processed. What you see is the whole of it.
Everything runs client side, which is the only arrangement where a privacy claim is checkable. Open the network tab and watch it stay empty.
You will find it under Clocks, alongside 7 other tools for the same sort of job.
Shows days, hours, minutes, and seconds breakdown.
2026-01-01T00:00:00Z
235d 9h 36m 21s ago The date 2026-01-01T00:00:00.000Z has already passed. Days: 235 Hours: 5649 Minutes: 338976 Seconds: 20338581
Yes. It is JavaScript running in this tab, so once the page has loaded it needs nothing further from the network. Put the machine in flight mode and it carries on. Nothing you do here is sent anywhere, because there is nowhere for it to go.
No. Reload the page and it starts from nothing. There is no account, no saved state and no cookie holding your last session. That is a deliberate trade: it cannot lose your data because it never keeps any.
Timing comes from performance.now(), the high resolution clock the browser provides, rather than from setInterval, which drifts by a few milliseconds every tick and compounds over minutes. What can still shift things is the browser throttling a tab in the background, so leave it visible if the timing matters.
Where a sound makes sense, it is generated with the Web Audio API rather than loaded as a file, so there is nothing to download and nothing to block. Browsers refuse to start audio until you have interacted with the page, which is why the first press is what switches it on.
Yes. The controls are sized for touch and the layout collapses to one column on a narrow screen. Bear in mind that a phone locking its screen will suspend the page, and timing stops with it.