Unix Timestamp
Interpret seconds, milliseconds, and ISO dates in UTC and local time.
Runs in your browser. Nothing is uploaded.
Unix seconds and milliseconds
Unix timestamps count seconds from 1970-01-01 00:00:00 UTC. Ten-digit values are usually seconds, while thirteen-digit values are usually milliseconds.
Current Unix seconds are usually ten digits. Current Unix milliseconds are usually thirteen digits. The same instant therefore appears as a much larger number in JavaScript, where Date.now() returns milliseconds. A value with the wrong unit can land decades away from the intended date, so check the result rather than relying only on digit count.
Nothing is uploaded while you convert. JWT exp, nbf, and iat claims are normally Unix seconds, so you can inspect them with the JWT Decoder. If a claim looks like milliseconds, verify the issuer's contract before converting it.
UTC is the reference point
Unix time counts from 1970-01-01 00:00:00 UTC. It is not a local clock reading and it does not change when daylight saving rules change. This page displays the UTC result and a local-time result for your browser's time zone.
ISO 8601 input can include a Z suffix or an explicit offset. Read that offset before comparing a date with a timestamp. A local date with no offset can be ambiguous in other tools, so use an explicit UTC value when you are writing logs or an API contract. The guide Unix timestamps explained includes examples for both units.
Use timestamps as values, not explanations
A timestamp tells you when an event was represented, not why it happened or whether a request was authorized. Keep the original value when debugging, record the unit in your schema, and avoid converting back and forth repeatedly. For token claims, inspect the surrounding header and payload with the JWT Decoder before drawing a security conclusion.
FAQ
Does timestamp conversion contact a time service?
No. The converter uses JavaScript Date and Intl functions in your browser to calculate UTC and local displays. The timestamp is never uploaded, and no remote clock is queried.
What is a Unix timestamp?
A Unix timestamp represents elapsed time from 1970-01-01 00:00:00 UTC. This page accepts seconds, milliseconds, microseconds, and nanoseconds when their input has the supported digit length.
Which timestamp inputs are accepted?
Numeric input must contain 10 digits for seconds, 13 for milliseconds, 16 for microseconds, or 19 for nanoseconds, with an optional leading minus sign. ISO input can be a YYYY-MM-DD date or a matching date and time with an optional UTC offset; a missing offset is treated as UTC.
How do I tell seconds from milliseconds?
A current Unix timestamp in seconds is usually 10 digits, while milliseconds are usually 13 digits. If a value is ambiguous, compare the converted date with the expected time before storing it.
Does this tool use UTC?
Yes. The UTC output is created with Date.toISOString, and the page also formats the same instant in the browser's local time zone. The local display does not change the Unix value.
What does the Relative result mean?
Relative compares the converted instant with the current time at conversion and reports rounded seconds, minutes, hours, or days as ago or in the future. The UTC and local outputs remain absolute timestamps even when the relative label changes.