Unix Timestamp Converter
Convert unix timestamps to human dates and back, with relative time
About this tool
Unix time counts seconds since 1970-01-01T00:00:00 UTC, and it shows up everywhere: database rows, JWT claims, log files, API responses. This converter accepts a timestamp in seconds or milliseconds — it detects which by magnitude — as well as ISO 8601 strings and most human-readable dates, and shows every representation at once: ISO, UTC, your local time, relative time, and both unix precisions.
The unit ambiguity is the classic trap: 1700000000 is November 2023 in seconds but January 1970 in milliseconds. The detected unit is displayed explicitly, and you can override it with one click when the guess is wrong — no more mentally counting digits.
Conversion is instant and local, and the current-time display keeps ticking so the page doubles as an epoch clock while you work.
Frequently asked questions
- How does the tool decide between seconds and milliseconds?
- By magnitude: values of 11 digits or more are treated as milliseconds, shorter ones as seconds. That maps seconds to years up to ~5138 and milliseconds from ~1973 onward, which resolves every realistic modern timestamp unambiguously. You can flip the unit manually for edge cases.
- What happens after 2038?
- The year-2038 problem affects systems that store unix time in a signed 32-bit integer. JavaScript numbers are 64-bit floats, so this converter handles dates far beyond 2038 — well past the year 275760, the JavaScript Date limit.
- Can I convert a date back to a timestamp?
- Yes. Paste an ISO 8601 string like 2026-07-20T12:00:00Z, or most conventional date formats, and the unix seconds and milliseconds appear alongside the other representations.
- Which timezone is used for the local time row?
- Your browser's configured timezone, via the Intl API — nothing is looked up remotely. The timezone name is printed next to the value so screenshots stay unambiguous.