Convert Unix timestamps to human-readable dates and back — local, UTC and ISO 8601, in your browser.
A Unix timestamp (or epoch time) is the number of seconds elapsed since midnight UTC on January 1st, 1970 — the convention virtually every operating system, database and API uses to store moments in time free of time-zone ambiguity. The catch is that a number like 1735689600 means nothing to a human, and half the systems you meet use seconds while the other half (JavaScript included) use milliseconds. This converter translates in both directions and shows every representation you might need at once: your local time, UTC, the ISO 8601 string and a relative description like "3 days ago".
Detection between seconds and milliseconds is automatic, by magnitude: a value of 100 billion seconds would correspond to the year 5138, so anything that large is treated as milliseconds — and the tool always states which interpretation it used, so there is no silent guessing. Conversion relies on your browser's native date engine, which applies your operating system's time zone and daylight-saving rules to produce the local reading, while the UTC and ISO 8601 lines stay universal. The relative line uses the browser's own internationalization formatter, so it comes out in natural language ("yesterday", "in 2 months") in the page's language.
The reverse direction takes a date and time from a native picker, interprets it in your local time zone, and returns the epoch in both seconds and milliseconds — the exact values to paste into code, a database query or an API call. Typical uses: decoding created_at fields from logs and JSON payloads, checking token expiry times, building test fixtures, or figuring out whether that cron job really fired when you think it did. Everything runs locally: no timestamp you convert is ever sent anywhere.
It is the number of seconds since January 1st, 1970, 00:00 UTC — the "Unix epoch". Systems use it because a single integer represents a moment unambiguously, regardless of time zones or calendar formats.
By size: current dates are 10 digits in seconds (about 1.7 billion) and 13 digits in milliseconds. The tool detects this automatically — values of 100 billion or more are treated as milliseconds — and always shows which interpretation it used.
Almost always a time-zone difference: this tool shows both your local time and UTC, while servers usually log in UTC or in the machine's configured zone. Compare the UTC line with your log to remove the ambiguity.
The year-2038 problem affects systems that store timestamps in signed 32-bit integers, which overflow on January 19th, 2038. This converter uses JavaScript numbers and handles dates hundreds of thousands of years in both directions.
No. All conversion runs 100% in JavaScript on your device, using your browser's own date engine. Nothing is transmitted, logged or stored.
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