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Unix Timestamp Converter

Paste Unix seconds, milliseconds, or an ISO-8601 string. Auto treats up to 10-digit numbers as seconds and 13-digit numbers as milliseconds.

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How to convert Unix time

  1. Paste Unix seconds, milliseconds, or an ISO-8601 datetime. Empty uses now.
  2. Auto treats up to 10-digit numbers as seconds and 13-digit numbers as milliseconds.
  3. Read UTC ISO, HTTP / RFC 1123, RFC 5322, SQL UTC, local, relative, seconds, and milliseconds.
  4. Use Now to fill the current Unix seconds from this device.

Unix time

Seconds or milliseconds since 1970-01-01T00:00:00Z

Auto seconds0 and integers with at most 10 digits
Auto millisecondsIntegers with 13 or more digits
ISO-8601Date.toISOString() in UTC
HTTP / RFC 1123IMF-fixdate in GMT
Leap secondsJavaScript Date POSIX model, not leap-second aware

What Unix time is

Unix time counts SI seconds from the 1970 UTC epoch, ignoring leap seconds the way JavaScript Date does. This page uses that Date model, not a leap-second-aware timescale. Apple CF Absolute Time (seconds from 2001-01-01) is not auto-detected; convert that on a dedicated converter later.

Seconds vs milliseconds

Auto matches the usual epoch-converter rule: 10-digit values are seconds (current Unix time), 13-digit values are milliseconds. Zero is seconds. 11-digit and 12-digit magnitudes are rejected in Auto so they are not silently multiplied. Force Unix seconds or Unix milliseconds when you know the unit.

Output fields

UTC ISO-8601 is always Zulu. HTTP / RFC 1123 is the GMT IMF-fixdate used in headers. SQL UTC is YYYY-MM-DD HH:mm:ss UTC. Local is this device's clock string. For a named IANA zone, use the time zone converter.

Unix timestamp questions

Does this page upload what I type?
No. The work runs in the page you opened. CZNull does not receive the input.
Why did Auto reject my number?
Values that are not clearly at most 10 digits (seconds) or 13+ digits (milliseconds) are treated as ambiguous. Choose a unit.
Leap seconds?
JavaScript Date does not apply leap seconds. Neither does this page.
ISO with an offset?
Pasting an ISO-8601 string uses Date parsing. Numeric Unix values are absolute instants and do not need a zone to interpret.
CF Absolute Time?
Not in Auto. That count starts at 2001-01-01 UTC, not 1970.