ISO 8601 format reference
- • YYYY-MM-DD — date
- • YYYY-MM-DDTHH:mm:ss — datetime (local)
- • YYYY-MM-DDTHH:mm:ssZ — datetime (UTC)
- • YYYY-MM-DDTHH:mm:ss±HH:mm — datetime (offset)
- • YYYY-Www-D — week date (Mon=1)
- • YYYY-DDD — ordinal date (day of year)
- • P1Y2M3DT4H5M6S — duration
What Is ISO 8601?
ISO 8601 is the international standard for date and time representation. It was designed to eliminate ambiguity: formats like YYYY-MM-DD sort correctly as text and are understood globally. The standard covers dates, times, datetimes, timezone offsets, week dates, ordinal dates, and durations.
Developers use ISO 8601 for APIs, databases, and log files. Most programming languages and frameworks support parsing and formatting ISO 8601 strings. This validator helps you verify that your date strings conform to the standard.
Common ISO 8601 Format Variants
Date only: 2024-01-15. Datetime with UTC: 2024-01-15T12:00:00Z. Datetime with offset: 2024-01-15T12:00:00+05:30. Week date: 2024-W03-1 (Monday of week 3). Ordinal date: 2024-015 (15th day of 2024). Duration: P1Y2M3DT4H5M6S (1 year, 2 months, 3 days, 4 hours, 5 minutes, 6 seconds).
Each variant has specific rules. The validator detects which variant you used and parses it accordingly. Invalid formats (wrong separators, out-of-range values) are rejected.
Converting Between Formats
Once a valid ISO 8601 string is parsed, the tool shows it in multiple formats: ISO 8601 (UTC), local time string, and Unix timestamp. This helps you verify the parsed value and convert between representations. The Unix timestamp is always in seconds since 1970-01-01 00:00:00 UTC.
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