Unix Timestamp Converter

A Unix timestamp is just a count of seconds since 1 January 1970 — compact for computers, unreadable for humans. This converter turns any epoch value into a full date in both UTC and your local time, and turns a date back into a timestamp. It auto-detects seconds versus milliseconds so you do not have to guess.

Local
UTC
ISO 8601
Relative
Interpreted as

Seconds
Milliseconds

How to use the Unix Timestamp Converter

The top panel converts a timestamp into a date. Paste an epoch value and it is shown in your local timezone, in UTC, as an ISO 8601 string, and as a human relative time ("3 months ago"). Leave the unit on Auto-detect and the tool decides whether your number is in seconds or milliseconds based on its magnitude; switch to Seconds or Milliseconds to force one. The Now button fills in the current timestamp.

The bottom panel goes the other way: pick a date and time and read off the corresponding Unix timestamp in both seconds and milliseconds, with a button to copy the seconds value. The date picker uses your local timezone, so the timestamp reflects the instant you selected wherever you are.

All conversion happens in your browser using its built-in date handling, so results match what your own code would compute and nothing is transmitted.

What a Unix timestamp is

A Unix timestamp (also called epoch time or POSIX time) is the number of seconds that have elapsed since midnight UTC on 1 January 1970, the "Unix epoch." It is the lingua franca of time in computing: a single integer with no timezone, no locale, and no ambiguity about format. Because it is just a number, it is trivial to store, compare, sort, and do arithmetic on — finding the duration between two events is a simple subtraction. That simplicity is why timestamps appear in databases, log files, APIs, JWT expiry claims, file metadata, and countless other places.

The most common point of confusion is the unit. Classic Unix time counts whole seconds, but many systems — JavaScript's Date.now(), Java, and lots of APIs — count milliseconds since the same epoch. A seconds value for a recent date is ten digits; the millisecond value is thirteen. Feeding a millisecond timestamp into a tool expecting seconds lands you tens of thousands of years in the future, which is exactly the kind of bug this converter's auto-detection is meant to prevent.

A timestamp represents an absolute instant, but a human date only makes sense with a timezone, which is why this tool shows both UTC and your local time. The same epoch value is, say, an evening in New York and the following morning in Tokyo — the instant is identical, the wall-clock reading differs. It is also worth knowing that the traditional 32-bit signed representation overflows on 19 January 2038 (the "Year 2038 problem"); modern systems use 64-bit values that push that limit billions of years out, so in practice you rarely need to worry about it.

Common use cases

  • Reading log and database values. Turn a raw epoch field into a date you can actually interpret, in your own timezone.
  • Debugging APIs and tokens. Decode timestamps in JSON responses or JWT exp/iat claims to check expiry and issue times.
  • Generating timestamps. Pick a date and grab the exact epoch value to paste into code, a query, or a test fixture.
  • Spotting unit mistakes. Confirm whether a value is in seconds or milliseconds when a date comes out wildly wrong.

Frequently asked questions

Is my timestamp in seconds or milliseconds?
A recent seconds timestamp has 10 digits; the millisecond version has 13. Auto-detect uses the magnitude to choose, and the "Interpreted as" line tells you which it used.

Why show both UTC and local time?
A timestamp is an absolute instant with no timezone. The same value reads as different wall-clock times around the world, so both UTC and your local time are shown to avoid confusion.

What is the Year 2038 problem?
Systems storing Unix time as a signed 32-bit integer overflow on 19 January 2038. Modern 64-bit timestamps avoid it entirely, so it rarely matters in current code.

Does the date picker use my timezone?
Yes. The Date → Timestamp panel interprets the date and time you pick in your local timezone and converts it to the corresponding UTC-based epoch value.