Date & TimeLOCALRuns in your browser
ISO 8601 Date Converter
Expand any date or timestamp into ISO 8601 forms — canonical UTC, basic format, week date, ordinal date — plus its calendar breakdown.
This tool handles input and primary processing in your browser and is designed not to send the input to QuickKit’s server.
Representations
| Canonical UTC | — |
|---|---|
| UTC without milliseconds | — |
| Basic format | — |
| Calendar date | — |
| Time of day (UTC) | — |
| Week date | — |
| Ordinal date | — |
| Unix seconds | — |
| Unix milliseconds | — |
| Weekday | — |
| ISO week | — |
| Day of year | — |
| Quarter | — |
| Source offset | — |
How it works
Input can be an ISO 8601 date (2025-01-01), a full timestamp with offset (2025-01-01T09:30:00+09:00), or a Unix timestamp in seconds or milliseconds. A value with no timezone offset is read as UTC and marked accordingly. Week numbers follow ISO 8601 (weeks start on Monday; week 1 contains the year's first Thursday), so early-January dates can belong to the previous week-year.