Unix Timestamp Converter

How does the tool decide between seconds and milliseconds?

By size. A number whose absolute value is above 10,000,000,000 is read as milliseconds and anything smaller as seconds. In practice that means 10-digit values such as 1700000000 are seconds and 13-digit values such as 1700000000000 are milliseconds, and the result shows a "Detected unit" row so you can check. Microsecond values (16 digits) are not recognised: they are read as milliseconds and land in the year 55840.

What time zone is used when I type a date without an offset?

UTC. A value like 2023-11-14T22:13:20, with or without a space instead of the T, is treated as UTC and converts to 1700000000, and the result says "Interpreted as: UTC (no offset given)". If you add an offset, as in 2023-11-14T22:13:20+05:30, the offset is honoured and the timestamp becomes 1699980200. A date alone, such as 2024-02-29, means midnight UTC.

Which date formats are accepted in Date → Timestamp mode?

ISO 8601 style text such as 2023-11-14, 2023-11-14T22:13:20Z or 2023-11-14T22:13:20+05:30. Regional formats such as 14/11/2023 are rejected with an error, because day-month and month-day order cannot be told apart reliably. Other free-form text may be accepted or refused depending on your browser’s date parser, so stick to ISO 8601 when the result matters.

Can I convert 0 or a negative timestamp?

Yes. 0 gives Thu, 01 Jan 1970 00:00:00 GMT and -86400 gives Wed, 31 Dec 1969 00:00:00 GMT. Fractional seconds are fine too: 1700000000.5 shows as 2023-11-14T22:13:20.500Z, while the whole-second figure is rounded down to 1700000000.

Why does the Local Date & Time row differ from the UTC row?

The local row uses the time zone and language settings of the device you are viewing the page on, so it changes from person to person. The UTC and ISO 8601 rows are the same for everyone and are the ones to copy into logs, tickets or code.

What exactly happens at the 2038 limit?

A signed 32-bit counter tops out at 2147483647, which is 03:14:07 UTC on 19 January 2038. One second later, 2147483648, is 03:14:08 on the same day, and this converter shows that correctly because it uses larger numbers. The problem is in systems that store the value in 32 bits, not in the conversion. Paste a suspect value from a database column to see which dates are affected.

Does the converter account for leap seconds?

No. Unix time pretends every day has exactly 86,400 seconds, and so does this tool, so a timestamp is simply a count of those days from 1 January 1970 UTC. That is also why it cannot tell you the true elapsed time between two dates that span a leap second.

What does the Current timestamp mode read from?

Your device’s clock at the moment the page calculates. If your clock is wrong, the timestamp is wrong by the same amount. It shows seconds, milliseconds, UTC, local time and ISO 8601 together.