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ISO 8601 Date Converter

Parse ISO 8601 strings and build them from a date, time and zone.

Parse an ISO 8601 string

Accepted: date-only · T separator · optional seconds and fraction · Z or ±HH:MM offsets.

Build an ISO string

How it works

  1. ISO 8601 writes one moment as YYYY-MM-DDTHH:MM:SS plus an optional fraction and offset; Z means UTC, and +05:30 means local time 5 h 30 m ahead of UTC.
  2. Parsing: strings with an offset identify one exact instant; the tool normalizes them to UTC, shows the Unix timestamps, and renders the instant in UTC and your local zone.
  3. Building: your date, time and zone are resolved to an instant (daylight saving included), then emitted with that zone’s offset, plus the UTC (Z) form and Unix seconds for cross-checking.

Good to know

  • Offset-less strings (2026-10-28T14:30:00) are shown as written with both the UTC and your-zone interpretations, never silently assumed to be one or the other.
  • Date-only strings (2026-10-28) are reported as dates; the implied midnight zone differs across systems, which the tool states rather than guessing.
  • RFC 3339 is the internet profile of ISO 8601 that APIs actually use; strings like 2026-10-28T14:30:00Z satisfy both standards.
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Frequently asked questions

What does the “Z” in an ISO string mean?
Zulu, meaning the string refers to UTC. 2026-10-28T14:30:00Z is 14:30 UTC. A string with +02:00 instead describes local time two hours ahead of UTC; both denote a precise instant.
What if my ISO string has no offset at all?
Then it is ambiguous: 14:30 somewhere, but where? The tool shows it as written and explains that an offset (or Z) is required to pin down an instant, rather than silently assuming one.
Is ISO 8601 the same as RFC 3339?
RFC 3339 is an internet profile of ISO 8601, representing a subset with a fixed layout. Strings like 2026-10-28T14:30:00Z satisfy both specifications.