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RFC 3339 / ISO 8601 Converter

Normalize Unix timestamps and explicit-offset date strings without guessing the timezone

Note: This page keeps timezone handling explicit. If you paste a bare local time without Z or an offset, it warns instead of guessing.
Normalize Unix or RFC 3339 timestampsPaste Unix seconds, milliseconds, or microseconds, or paste an RFC 3339 / ISO 8601 string with an explicit offset, then copy the normalized UTC result
Accepted numeric inputs: seconds, milliseconds, or microseconds. String inputs must include Z or an explicit offset.
What It Normalizes

The page accepts Unix timestamps in seconds, milliseconds, or microseconds, plus RFC 3339 / ISO 8601 strings with explicit offsets. It normalizes the value to UTC and shows copy-friendly Unix outputs at the same time.

Normalize a Timestamp
  1. Paste one numeric timestamp or one RFC 3339 / ISO 8601 string.
  2. Click Normalize timestamp to detect the unit or offset.
  3. Copy the normalized UTC output when an API or log format expects RFC 3339.
  4. Use the Unix values when another system still expects epoch time.
Why Explicit Offsets Matter

A timestamp like 2026-04-04T13:31:09 is ambiguous because it does not say which timezone the clock reading belongs to. This page asks for Z or an explicit offset so the normalized UTC value means the same thing in every environment.

FAQ
Why reject 11-digit or 12-digit numeric input?

Because those lengths are ambiguous. They can look like short millisecond values or extremely large second values, so this page asks you to be explicit.

Does it preserve microseconds everywhere?

The Unix microseconds field preserves them, but browser date rendering is still millisecond-based. The page warns when sub-millisecond precision is dropped from the displayed RFC 3339 strings.

Is any of this sent to a server?

No. Detection and normalization run locally in your browser.