How to Convert a Timestamp to a Date (and Back)

To convert a timestamp to a date, paste the value into a converter — it detects seconds versus milliseconds automatically and shows the moment in your local time, in UTC, and as an ISO 8601 string. To go the other way, pick a date and copy the matching timestamp in seconds or milliseconds.

This guide is written for developers debugging logs, APIs, databases and JWT expiry claims, and covers how detection works, what ISO 8601 means, and why a converted date can differ from what your server logged.

Why timestamps trip developers up

A Unix timestamp is a compact way to store an instant, but it hides two ambiguities that cause bugs: the unit (seconds or milliseconds) and the display zone (local or UTC). Mistake a millisecond value for seconds and your date lands 50,000 years in the future; read a UTC log in local time and you chase a phantom offset. A converter that resolves both at a glance saves real debugging time when you are staring at a log line or an API response.

How to convert timestamps in your browser

1. Copy the live current timestamp from the top of the tool, or paste any timestamp into the converter — the unit is detected for you.
2. Read the result in local time, UTC and ISO 8601 side by side.
3. To reverse the conversion, pick a date and time (or press Now to fill the current moment).
4. Copy the resulting timestamp in seconds or milliseconds with one click.

Seconds, milliseconds and ISO 8601 at a glance

Knowing the shape of each format makes debugging faster:

Format	Looks like	Where you see it
Seconds	10 digits (~1.7 billion)	Unix tools, most APIs
Milliseconds	13 digits	JavaScript Date.now()
ISO 8601	2026-07-04T12:30:00.000Z	APIs, databases, logs

The trailing Z in an ISO 8601 string means UTC, and the format sorts correctly as plain text — which is why systems prefer it for stored timestamps.

Key features

• Bidirectional: timestamp to date and date to timestamp.
• Auto-detects seconds versus milliseconds input.
• Shows local time, UTC and ISO 8601 simultaneously.
• Live ticking current timestamp with copy buttons.
• "Now" button fills the date picker instantly.
• Runs entirely in your browser — safe for production data, works offline.

Try the Timestamp Converter now — it's free and runs entirely in your browser.

Frequently asked questions

How do I convert a timestamp to a date?

Paste the timestamp into the input. The tool multiplies seconds by 1000 if needed, builds a date from the milliseconds, and shows it in your local zone, in UTC and as ISO 8601.

How can I tell if a timestamp is in seconds or milliseconds?

Current second timestamps are 10 digits and millisecond timestamps are 13. The converter checks the magnitude automatically, treating a 13-digit value as milliseconds and a 10-digit one as seconds.

What is ISO 8601 format?

It is the international standard for writing dates and times, such as 2026-07-04T12:30:00.000Z. The Z means UTC. It is unambiguous across regions and sorts correctly as text, which is why APIs and databases favour it.

Why does the converted date differ from my server log?

Almost always a zone difference. This tool shows both your local time and UTC for the same instant; servers usually log in UTC, so compare against the UTC line rather than the local one.

Are timestamps affected by time zones?

No. A Unix timestamp marks one absolute instant worldwide — only its human-readable form changes by zone. That is exactly why systems store timestamps and convert to local time only for display.

Related free tools

• Unix Timestamp Converter — dedicated epoch time with unit control.
• Time Zone Converter — convert times across world zones.
• Date Difference Calculator — measure the gap between two dates.
• JWT Decoder — inspect token claims including expiry timestamps.

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