About the ISO 8601 Date Converter
ISO 8601, like 2026-09-05T08:30:00.000Z, is the unambiguous, sortable date format that APIs, databases and data interchange rely on, because it avoids the day/month confusion of local formats and sorts correctly as text. This tool converts a Unix timestamp or a date in almost any format into ISO 8601, and can also output the RFC 2822 form, a local string, or the date alone.
The format has traps that cost real debugging time. The trailing Z means UTC, and a string with no zone at all, such as 2026-09-05T08:30:00, is read as local time by most parsers, so the same value lands hours apart on a laptop in Berlin and a server in Virginia. A date-only string such as 2026-09-05 goes the other way in JavaScript and is treated as midnight UTC, which is why a stored birthday can display as the previous day for anyone west of Greenwich. Keeping an explicit offset removes both problems, and the ISO output here always carries one.
The everyday job is cleaning a column where dates arrived in three different shapes at once, 05/09/2026 from a European export, Sep 5 2026 from a log and 1725500000 from an API, and every row has to go into the same database field. Paste the lot, one per line, and they come back identical in form. For a custom pattern instead, use the Date Format Converter; to read a timestamp in every form, the Unix Timestamp Converter; to see which ISO week a normalised date falls in, the Week Number Calculator.
How to use
- Paste timestamps or dates, one per line.
- Choose the output form.
- Copy the ISO 8601 dates.
Common questions
- Why use ISO 8601?
- It is unambiguous and sorts correctly as text, which is why APIs and databases prefer it.
- Is the output in UTC?
- The ISO and RFC options are in UTC (Z). The local option uses your time zone.
- Can it read a Unix timestamp?
- Yes, in seconds or milliseconds.