How it works
What a Unix timestamp is
A Unix timestamp counts the seconds elapsed since 1 January 1970, 00:00:00 UTC — the Unix epoch. It carries no time zone: the same timestamp names the same instant everywhere, which is exactly why it is the right thing to store in a database and the wrong thing to show a user.
Negative values are valid and refer to dates before 1970.
Seconds or milliseconds?
Unix tooling, most APIs and date +%s use seconds. JavaScript's Date.now(), Java and many logging systems use milliseconds. Mistaking one for the other throws you off by a factor of 1,000 — a 2026 timestamp read as milliseconds lands in 1970.
This tool detects the unit by magnitude: values with 12 or more digits are treated as milliseconds. You can override that if you need to.
The 2038 problem
A signed 32-bit integer can only count to 2,147,483,647, which as a second count runs out on 19 January 2038. Systems still storing timestamps in a signed 32-bit field will overflow then, the same class of bug as Y2K. Modern systems use 64-bit timestamps, which push the limit far past any practical concern.
What people use it for
- Reading a log line or database row that stores time as an integer.
- Debugging a token's expiry — JWT
expandiatclaims are Unix timestamps in seconds. - Checking a cache header or a scheduled job's next-run value.
- Converting a date into a timestamp for an API query parameter or a
WHEREclause. - Confirming a time zone assumption by comparing the UTC and local renderings side by side.
Nothing is uploaded. This tool runs entirely in JavaScript in your browser. Your input is never sent to a server, never logged and never stored, and no account is required. Once the page has loaded you can go offline and it still works — open your browser's network tab and watch if you'd like to confirm it.
Frequently asked questions
Is the epoch timestamp in UTC?
Yes. A Unix timestamp is an absolute count of seconds since 1970-01-01 00:00:00 UTC and carries no time zone. The local time shown here is your browser's interpretation of that same instant.
How do I tell seconds from milliseconds?
By length. A current timestamp in seconds has 10 digits; in milliseconds it has 13. This tool treats anything with 12 or more digits as milliseconds, and you can override the unit.
Does it handle leap seconds?
No, and neither does Unix time itself. Unix time deliberately ignores leap seconds, so every day is treated as exactly 86,400 seconds. This is a property of the format, not a limitation of this tool.
What is the ISO week number?
The week of the year under ISO 8601, where weeks start on Monday and week 1 is the week containing the first Thursday of January. It is the week numbering used in most of Europe and in many reporting systems.
Can I convert a date in my own time zone?
Yes. Enter a date without a Z or offset and your browser interprets it as local time. Add Z to force UTC, or an offset like +05:30 to be explicit.
Tools that run where your code is
This page does its work in your browser because sending your data to a server to process it is a bad default. Catalase applies the same idea to AI coding: a free, open-source code editor that runs language models on your own machine through Ollama, with no account and no telemetry. Cloud models are there when you choose one, not by default.
Related tools
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