Tools / Time converter
Unix timestamp and ISO 8601 converter
Enter a Unix timestamp or an ISO 8601 date-time. Numbers are read as seconds or milliseconds by size; the result is shown in UTC and in a time zone you choose.
Examples:
Seconds or milliseconds
A number with an absolute value of 10^11 or more is read as milliseconds, anything smaller as seconds. Ten-digit values are seconds and thirteen-digit values are milliseconds, which covers what logs and APIs produce today. Millisecond timestamps from the first few years after the epoch are the exception: they are small enough to be misread as seconds. If the result lands thousands of years away, the guess was wrong.
Pitfalls
An ISO string without an offset is ambiguous. JavaScript's Date.parse reads 2026-10-07 as UTC midnight but 2026-10-07T09:30 as local time. This tool reads both as UTC and says so. Add Z or an offset such as +02:00 to be explicit.
An offset is not a time zone. +02:00 describes one instant; Europe/Berlin is a set of rules that changes its offset twice a year. Store instants in UTC and keep the zone name separately if you need local time later.
Unix time ignores leap seconds. Every day is exactly 86400 seconds long, so subtracting two timestamps ignores any leap seconds in between; over long spans the result can be off by that many seconds.