Unix Timestamp Converter

What this tool does

A Unix timestamp counts the seconds elapsed since 00:00:00 UTC on 1 January 1970, ignoring leap seconds. That makes it compact and unambiguous for machines and completely unreadable for people. Paste one here and you get the instant it represents in UTC, in your own zone, and in the three string formats you are most likely to need to paste back somewhere else.

The second half of the page runs the other way: pick a date and time, say whether you mean it in your local zone or in UTC, and read off the epoch value in seconds and milliseconds.

Common uses

• Reading a log line. Structured logs from Go, Java and most observability pipelines emit raw epoch values, often in milliseconds or nanoseconds.
• Checking a JWT. The exp, iat and nbf claims are epoch seconds — pasting exp here tells you at a glance whether a token has already expired.
• Building a fixture. A test that needs a stable "yesterday" wants a literal number, not Date.now().
• Comparing a database column against an API response when one stores seconds and the other milliseconds.

A short example

The value 1700000000 resolves to:

UTC        2023-11-14 22:13:20
ISO 8601   2023-11-14T22:13:20.000Z
RFC 2822   Tue, 14 Nov 2023 22:13:20 +0000
Epoch ms   1700000000000

How the unit is detected

The unit is inferred from the digit count, which is exact rather than a guess for anything recorded this century. Since 9 September 2001 every timestamp in seconds has had 10 digits and every timestamp in milliseconds 13, and that stays true until November 2286. So:

• up to 11 digits — seconds
• 12 to 14 digits — milliseconds
• 15 to 17 digits — microseconds, as PostgreSQL and ClickHouse emit
• 18 or more — nanoseconds, as Go's UnixNano and OpenTelemetry emit

The cutoff sits at 12 digits because 100,000,000,000 seconds is the year 5138 — a value no real system produces — whereas the same number of milliseconds is 1973. The detected unit is always shown, and the dropdown overrides it. Nanosecond values exceed the 2⁵³ limit of a JavaScript number, so they are converted with BigInt and any sub-millisecond remainder is reported rather than quietly discarded.

Worth knowing

Unix time is not a count of every second that has passed. Leap seconds are absorbed by repeating a value, so the 27 inserted since 1972 are invisible here — which is precisely why the format is easy to compute with. Negative values are legal and mean dates before 1970. And the year 2038 limit belongs to the 32-bit signed integer, not to the epoch itself: at 03:14:07 UTC on 19 January 2038 a time_t of that width overflows to 1901. Anything storing 64 bits is fine for the next 292 billion years.