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ISO 8601 date parser and converter

Parse an ISO 8601 datetime and convert it to UTC, local time and Unix timestamps.

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ISO 8601

🔒 Inputs are processed locally in your browser.

Result

How to use it

Parse an ISO-style date-time into UTC, the browser’s local time, Unix seconds and Unix milliseconds.

Enter a date-time beginning with a full date and T, such as 2026-09-02T10:30:00+09:00.
Select Parse.
Compare the normalized UTC, local display and Unix timestamps.

Expected shape: Starts with YYYY-MM-DDT
UTC output: Normalized UTC date-time
Unix seconds: milliseconds ÷ 1000, rounded down
Unix milliseconds: Milliseconds since 1970-01-01T00:00:00Z

10:30 in +09:00 becomes 01:30 UTC

2026-09-02T10:30:00+09:00 is normalized to 2026-09-02T01:30:00.000Z in UTC.

If you omit a timezone offset, browser date parsing can interpret the value as local time. Include Z or an explicit offset when the intended instant must be unambiguous.

Include a timezone when the exact instant matters

A value with Z or an explicit offset such as +09:00 identifies the intended instant clearly. If the timezone is omitted, the device can interpret the value as local time.

UTC and local output represent the same instant

The UTC line changes the displayed timezone, not the underlying moment. The Local line uses the timezone configured in the current browser/device.

Unix seconds and milliseconds share the same epoch

Both count from 1970-01-01T00:00:00Z; the millisecond value simply has three more digits of precision.

A parseable string is not automatically standards-perfect ISO 8601

The browser may accept variants beyond the strictest profile. Use a schema or standards validator when exact format compliance is the requirement.

Related references: ISO 8601 · Date formats · World calendars