Unix Timestamp Converter
Convert Unix seconds or milliseconds to an ISO 8601 UTC instant and show the reversible timestamp values. Inputs stay in your browser.
Unix time counts from 1970-01-01T00:00:00Z; the selected input unit is seconds.
Context matters.
- Unix timestamps identify UTC instants and do not contain a local time zone. Leap seconds are not represented by JavaScript Date.
Sources & scope
The calculation guide and this source trail show what the result means, where the rule came from and when it was last reviewed. This is source-and-calculation QA, not a claim of medical, legal, tax or other professional review; time-sensitive decisions still belong with the linked authority.
A visible path from input to answer.
Convert Unix seconds or milliseconds to an ISO 8601 UTC instant and show the reversible timestamp values. The page keeps the calculation scope and its limits beside the result so the output can be checked, copied or revisited.
- Read the record. The calculator uses Unix timestamp and Timestamp unit supplied in the form.
- Apply the scope. It applies the Global Unix epoch and ISO 8601 UTC representation reference and the explicit date, unit and counting conventions shown in the result.
- Expose the checkpoints. Intermediate rows, warnings and timeline events stay visible; the emphasized row identifies the primary checkpoint when one exists.
Unix time counts from 1970-01-01T00:00:00Z; the selected input unit is seconds.
- UTC / ISO 86012026-08-22T08:00:00.000Z
Calculation purpose: Convert Unix seconds or milliseconds to an ISO 8601 UTC instant and show the reversible timestamp values. This is a high-sensitivity reference output; the linked authority or qualified professional controls the final decision.
Numeric inputs are constrained by the field limits and the result keeps the entered units visible. Zero, minimum, maximum and non-finite values are treated as input boundaries.
Rule set 1.1.0 · Last reviewed 2026-08-22 · Next review due 2027-02-22. The source panel below contains the linked evidence.
What to know before using the result.
What time zone does a Unix timestamp use?
A Unix timestamp represents an instant counted from 1970-01-01 00:00:00 UTC; the displayed local time depends on the selected zone.
How can I tell seconds from milliseconds?
Modern millisecond timestamps usually have about thirteen digits, while second timestamps commonly have about ten. The input unit remains explicit.
Are leap seconds represented?
Conventional Unix time does not model leap seconds as distinct timestamp values.