Unix Timestamp Converter

About Unix Timestamp Converter

A Unix timestamp is the number of seconds since January 1, 1970 UTC (the epoch). This converter shows the current Unix time, turns any timestamp into a readable Local, UTC, and ISO 8601 date — auto-detecting seconds or milliseconds — and converts a date back into a timestamp. Everything runs in your browser instantly.

Seconds or milliseconds — how to tell

The single most common mistake is mixing the two units. Unix time proper counts seconds, and a present-day value is ten digits — 1750000000 is June 2025. JavaScript's Date.now(), and most JavaScript APIs, return milliseconds, which is thirteen digits. Feed a millisecond value into a seconds-based parser and you land tens of thousands of years in the future; do the reverse and you land in January 1970.

The quick check is digit count. Ten digits are seconds, thirteen are milliseconds, sixteen are microseconds (common in Python and some databases), and nineteen are nanoseconds (Go's UnixNano). If a date comes out as 1970 or as some year in the distant future, you almost certainly have a unit mismatch rather than a corrupt value.

Why timestamps have no time zone

A Unix timestamp is an instant, not a wall-clock reading. The same number refers to the same moment everywhere on earth; what changes is how you render it. 1750000000 is 03:06 in London and 22:06 the previous day in New York, and neither is more correct than the other.

This makes timestamps ideal for storing when something happened and poor for storing when something should happen. A meeting at 09:00 next March is not an instant yet — if the jurisdiction changes its daylight-saving rules between now and then, the correct instant moves. Store past events as timestamps; store future local appointments as a local date plus a time-zone name.

The 2038 problem

Systems that store Unix time in a signed 32-bit integer can represent up to 2,147,483,647 seconds, which runs out at 03:14:07 UTC on 19 January 2038. One second later the counter overflows to a large negative number and the date reads as December 1901. This is the same class of bug as Y2K, and it is not hypothetical for embedded devices, older file formats, and legacy database columns.

Modern languages and 64-bit systems use a wider integer and are fine for the next several billion years. The practical advice is to check any integer column that stores time: if it is a 32-bit int, it has a deadline. Anything computing a date more than a decade ahead — a mortgage term, a certificate expiry — can hit this well before 2038 arrives.

Leap seconds and ISO 8601

Unix time pretends leap seconds do not exist. It is defined as the number of seconds since the epoch assuming every day is exactly 86,400 seconds long, which is not quite true of real astronomical time. When a leap second is inserted, Unix time repeats or smears a second rather than counting it, so the difference between two timestamps is not always the exact elapsed physical time. For almost all software this is irrelevant, but it matters for high-precision timing.

ISO 8601 is the readable counterpart: 2025-06-15T14:30:00Z, where the trailing Z means UTC. It sorts correctly as plain text, which is why it is the right format for log files and file names, and it is unambiguous in a way that 06/15/2025 is not — that string means June in the United States and does not parse at all as a date in most of the rest of the world.

Frequently asked questions

Is the timestamp in seconds or milliseconds?

Unix time is in seconds (a 10-digit number today); JavaScript and many APIs use milliseconds (13 digits, 1000× larger). This tool auto-detects the magnitude and converts either correctly, so a date won't come out 50 years off.

How do I convert milliseconds to a date?

Paste the 13-digit millisecond value — it's detected automatically and converted to Local, UTC, and ISO 8601. No need to divide by 1000 yourself.

What time zone does the converter use?

Timestamps are absolute (UTC). The tool shows both the UTC date and your local time for the same instant, so you can read whichever you need.

What is the current Unix timestamp?

The card at the top shows the live current epoch time, ticking every second, and you can copy it with one click.

What is the year-2038 problem?

32-bit signed timestamps overflow in January 2038. This tool uses 64-bit numbers, so it isn't affected and converts dates far beyond 2038.