Unix Timestamp Converter

Convert between Unix timestamps and human-readable dates.

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Input
Output
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About unix timestamp converter

Unix Timestamp Converter needs nothing from a server once the page has loaded. Leave it open on a train with no signal and it carries on.

Paste a customer record into it if you need to. The record never leaves the machine you are sitting at.

You will find it under Date conversion, alongside 11 other tools for the same sort of job.

Supports seconds and milliseconds, shows ISO 8601 and UTC formats.

How to use it

01
Start it
Every control is on the tool itself. Keyboard shortcuts, where there are any, are listed beside it.
02
Watch it run
It updates in the page as you go. Nothing is sent anywhere, so it keeps working with the network off.
03
Close when done
Nothing is stored between visits. Reloading gives you a clean start rather than picking up where you left off.

Examples

Unix Timestamp to Date
Convert a Unix timestamp to a human-readable date
Input
1735689600
Output
Unix Timestamp (s):  1735689600
Unix Timestamp (ms): 1735689600000
ISO 8601:            2025-01-01T00:00:00.000Z
UTC:                 Wed, 01 Jan 2025 00:00:00 GMT
Local:               Wed Jan 01 2025 01:00:00 GMT+0100 (Central European Standard Time)
Date to Unix Timestamp
Convert an ISO date string to a Unix timestamp
Input
2025-07-04T12:00:00Z
Output
Unix Timestamp (s):  1751630400
Unix Timestamp (ms): 1751630400000
ISO 8601:            2025-07-04T12:00:00.000Z
UTC:                 Fri, 04 Jul 2025 12:00:00 GMT
Local:               Fri Jul 04 2025 14:00:00 GMT+0200 (Central European Summer Time)

Questions

Does Unix Timestamp Converter work offline?+

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.

Does it remember anything between visits?+

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.

Is it accurate?+

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.

Does it make a sound?+

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.

Can I use Unix Timestamp Converter on a phone?+

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.