Unix Timestamp Converter
Convert a Unix timestamp to a human date and back. Supports seconds and milliseconds, shows UTC, local time, ISO 8601 and a relative 'time ago' value.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Unix Timestamp Converter Works
This tool converts between Unix timestamps (epoch time) and human-readable dates in both directions. Paste a timestamp to see the date, or pick a date to get the timestamp. It handles both seconds (the classic 10-digit format) and milliseconds (the 13-digit format used by JavaScript and many APIs) automatically.
A Unix timestamp is the number of seconds since the epoch: midnight UTC on 1 January 1970. Because it is just a count of seconds, it has no time zone of its own — the same timestamp represents the same instant everywhere in the world.
The Formula
To turn a timestamp into a date, convert it to milliseconds since the epoch:
milliseconds = seconds × 1000 date = epoch + milliseconds
To go the other way, take the milliseconds since the epoch and divide:
seconds = milliseconds ÷ 1000
Worked Example
Take the timestamp 1700000000 (10 digits, so it is in seconds):
- Milliseconds = 1700000000 × 1000 = 1,700,000,000,000 ms
- That equals 2023-11-14T22:13:20Z in ISO 8601
- In UTC: 2023-11-14 22:13:20 UTC
To reverse it, the date 2023-11-14 22:13:20 UTC is 1,700,000,000,000 ms after the epoch, and 1,700,000,000,000 ÷ 1000 = 1700000000 seconds.
Seconds vs Milliseconds
| Format | Digits today | Example | Used by |
|---|---|---|---|
| Seconds | 10 | 1700000000 | Linux, databases, most APIs |
| Milliseconds | 13 | 1700000000000 | JavaScript Date.now(), many web APIs |
| Microseconds | 16 | 1700000000000000 | High-resolution logging |
If you mix up seconds and milliseconds you will be off by a factor of 1000 — a 2023 date can suddenly look like the year 56,895. Always check the digit count.
Why Engineers Use Unix Time
Storing time as a single integer is compact, easy to sort, easy to subtract (the difference is a duration in seconds), and free of time-zone and formatting ambiguity. Display logic then converts the timestamp to whatever local format the user expects. This separation of storage from display is why epoch time underpins databases, log files, JWTs, HTTP headers and countless APIs.
Frequently asked questions
What is a Unix timestamp?+
A Unix timestamp (also called epoch time or POSIX time) is the number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970, not counting leap seconds. For example, 1700000000 corresponds to 2023-11-14 22:13:20 UTC. It is a compact, timezone-free way to store a moment in time.
What is the difference between seconds and milliseconds timestamps?+
A standard Unix timestamp is in seconds and is 10 digits long today (e.g. 1700000000). JavaScript and many APIs use milliseconds, which is 13 digits (e.g. 1700000000000). This converter auto-detects: 13-digit values are read as milliseconds, shorter values as seconds.
How do I convert a timestamp to a readable date?+
Multiply the timestamp by 1000 to get milliseconds, then create a date from milliseconds since the epoch. This tool does it instantly and shows the result in UTC, your local time zone, ISO 8601 format and as a relative 'X ago / in X' value.
Does the converter use my local time zone?+
Yes. The 'Your local time' field and the date picker use your browser's time zone, while the UTC field is always in Coordinated Universal Time. The underlying Unix timestamp itself has no time zone — it is an absolute instant.
What is the year 2038 problem?+
Systems that store Unix time in a signed 32-bit integer can only count up to 2,147,483,647 seconds, which is reached on 19 January 2038. After that the value overflows. Modern systems use 64-bit timestamps, which avoid the problem for billions of years.