ISO 8601 Converter

Runs in browser Utilities

Validate ISO 8601 strings (with offsets, fractional seconds, week dates and durations like P1Y2M3D), explain each component, and convert to epoch or other formats.

Privacy: This tool runs entirely in your browser. Your input never leaves your device.

How to use ISO 8601 Converter

  1. Paste an ISO 8601 date-time, duration or interval.
  2. Choose the timezone to apply when the value has no offset.
  3. Review the components and copy the equivalent format you need.

ISO 8601 Converter features

  • Parses calendar, week and ordinal dates, basic and extended formats, fractions and offsets
  • Durations (P1Y2M3DT4H5M6S, PT30M, P2W) with human text and totals
  • Intervals: start/end, start/duration, duration/end and repeating R5/…
  • Component-by-component explanation with validation messages
  • Equivalent formats: RFC 3339, basic, week date, ordinal date, RFC 2822, epoch
  • "Generate from now" for the current instant in every form

ISO 8601 Converter example

Parse a timestamp with an offset

Input:

2024-03-15T13:30:00.250+03:00

Output:

Year 2024 · Month 03 · Day 15 · 13:30:00.250 · Offset +03:00
RFC 3339 UTC: 2024-03-15T10:30:00.250Z · Week date 2024-W11-5 · Ordinal 2024-075

Frequently asked questions about ISO 8601 Converter

What is the difference between ISO 8601 and RFC 3339?

RFC 3339 is a strict profile of ISO 8601 used on the internet: always a full date and time, a "T" separator (a space is tolerated) and a mandatory Z or ±hh:mm offset. Every RFC 3339 string is valid ISO 8601, but not vice versa.

Which forms are supported?

Calendar dates (2024-03-15), basic format (20240315T103000Z), reduced precision (2024-03), week dates (2024-W11-5), ordinal dates (2024-075), times with fractions and offsets, durations (P1Y2M3DT4H5M6S, PT30M, P2W) and intervals (start/end, start/duration, duration/end, R5/…).

Why is a duration's total in seconds "approximate"?

Years and months have variable length, so the total uses 365-day years and 30-day months. Durations made only of weeks, days, hours, minutes and seconds are exact.

What does 24:00:00 mean?

ISO 8601 allows 24:00:00 to denote the end of a day, equal to 00:00:00 of the next day. The tool accepts it and normalises the output.