Unix Timestamp Converter
Convert Unix timestamps to dates and back across time zones in your browser, with batch support.
- Runs in your browser, files never leave your device
- Free, open source, no account, no ads
- Works offline after the first visit
Unix Timestamp Converter
Ctrl/⌘ + Enter converts · n fills in the current time
How it works
- Paste a timestamp or a date. Type a Unix value in seconds, milliseconds, microseconds or nanoseconds, or fill in year, month, day and time. The unit is detected from the digit count, and you can override it.
- Pick a time zone. Search the zone list or tick UTC. Results show UTC, your local time, the chosen zone, ISO 8601, RFC 2822 and a relative phrase, with notes for daylight saving gaps and overlaps.
- Copy or batch. Copy any row with one click, or switch to Batch, paste many lines (log lines work) and download the table as CSV. All of it is computed on your device.
Questions, answered
Are my timestamps sent anywhere?
No. Unix Timestamp Converter runs entirely in your browser. Everything you paste, including log lines, is converted with JavaScript on your device and never sent to a server. You can disconnect from the internet and it keeps working.
How does it know if a value is seconds or milliseconds?
By the number of digits before any decimal point: up to 11 digits is seconds, 12 to 14 is milliseconds, 15 to 17 is microseconds and 18 or more is nanoseconds. Today that means 10, 13, 16 and 19 digits. If the guess is wrong, pick the unit by hand. Microsecond and nanosecond values are parsed with BigInt, so the digits below one millisecond are kept and shown separately.
What happens with daylight saving time?
When you convert a date in a zone that shifts its clocks, the tool checks the offset on both sides of the change. If the time was skipped (clocks jumped forward) it says so and shows the next valid time. If it happened twice (clocks went back) it gives both timestamps.
What is the year 2038 problem?
Systems that store Unix time as a signed 32-bit number run out at 2147483647, which is 2038-01-19 03:14:07 UTC. The converter flags values beyond that limit, and also flags negative timestamps, which are dates before 1970-01-01. JavaScript dates reach the year 275760, and anything past that gets a range message.
Is it really free, and does it work offline?
Yes. It is open source under the MIT license, with no account, no limits and no ads. After your first visit the page is cached by a service worker, so it loads without a connection, and you can install it from your browser's menu as an app. If it saves you time, you can say thanks on Ko-fi.
Was this written by AI?
Yes. Unix Timestamp Converter was generated by Claude Code from a written specification inside an automated pipeline, with a test suite that runs in a real browser. The full source is on GitHub, so you can read every line before you trust it with your data.
Built by one person, given away for free
Unix Timestamp Converter is a free alternative to paid tools like EpochConverter and unixtimestamp.com. If it earns a place in your bookmarks, a coffee keeps the updates coming.
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