Unix Timestamp Converter Online — Free & Instant
Paste a Unix timestamp or a date string and read it in every format you actually need: ISO 8601, UTC, Unix seconds and milliseconds, and how far from now it is.
- Leave the unit on auto — 10-digit values are treated as seconds, 13-digit as milliseconds.
- The 'now' row gives you the current Unix time for log grepping and token math.
- ISO strings parse with or without the Z; naive strings are interpreted as local time.
Every conversion in this toolkit runs in your browser with the standard JS APIs. Your input is never uploaded, stored, or logged.
Seconds, milliseconds, and the 10^11 trick
The same number means different things depending on the unit: 1735689600 is 2025-01-01 in seconds, but in milliseconds it is 1970-01-21. The auto-detection rule is length: seconds timestamps for any realistic date have 10 digits (until the year 2286), milliseconds have 13. Values at or above 10^11 are treated as milliseconds.
Logs, APIs, and databases disagree about units constantly — Postgres and most Unix tooling use seconds, JavaScript's Date.now() and Java use milliseconds. Converting one into the other by hand is how you get logs claiming events happened in 1970.
Timezones: what the tool shows
Unix time is timezone-free — a count of seconds since 1970-01-01 UTC. The ISO output is therefore always UTC (the Z suffix). When a timestamp 'looks wrong by some hours', the timestamp is fine and your reading of it is local-time-adjusted; the UTC line here is the ground truth to compare against.
The relative line ('3 days ago', 'in 5 months') exists for the way you actually scan logs: noticing that a suspicious entry is 40 seconds before a deploy is easier than comparing ISO strings.
Frequently asked questions
Is 1735689600 in seconds or milliseconds?
Seconds — 10 digits, resolving to 2025-01-01T00:00:00Z. In milliseconds that number would be January 21, 1970. When in doubt, paste it here with the unit on auto and the detected interpretation is shown.
Why does my timestamp show a date from 1970?
A seconds timestamp was interpreted as milliseconds (or vice versa). 13-digit values are milliseconds, 10-digit are seconds — force the correct unit in the selector.
Is anything about my input sent to a server?
No. All conversion runs in your browser with the standard Date API.