Unix Timestamp Converter

What is a Unix timestamp?

A Unix timestamp is a single number representing a point in time: the number of seconds (or milliseconds) that have passed since January 1, 1970, 00:00:00 UTC — the "Unix epoch." It's the standard way most databases, APIs, and log files store a date, since a plain number is easy to compare, sort, and store without worrying about time zones or calendar formatting — until it needs to be read by a person, at which point it needs converting back into an actual date.

This tool converts in both directions at once: a "Timestamp → Date" field turns a Unix timestamp into a local date, a UTC date, an ISO 8601 string, and a custom format all simultaneously, a "Date → Timestamp" field does the reverse, and a free-text field parses almost any date string — ISO, RFC 2822, or a typed date — straight into its epoch value.

How to use it

How the conversion works

A timestamp is automatically treated as milliseconds if it's larger than about a trillion, since a 13-digit value is almost always milliseconds while a 10-digit value is almost always seconds — no manual unit toggle needed. Once parsed, the result is shown four ways at once: a long date and time in the selected output timezone (with a relative "X ago" description), a custom pattern built from YYYY, MM, DD, HH, hh, mm, ss, A, ddd, and MMM tokens, a UTC date and time, and an ISO 8601 string. Choosing a format preset — like "US 12-hour" or "Readable" — fills the custom pattern field with that preset's tokens, which can then be edited freely. The "Date → Timestamp" field reads a date and time in your local timezone and converts it back to the timestamp for that exact moment, and "Parse any date string" hands the raw text straight to JavaScript's own date parser, so it accepts most common date formats without needing to match a specific pattern.

Features & benefits

Why this runs entirely in your browser

Timestamps can reveal exactly when a private event happened, so nothing is uploaded. Every conversion uses JavaScript's built-in Date handling, running locally in the tab, which means it keeps working offline once the page has loaded.

A note on seconds vs. milliseconds

Unix timestamps are traditionally counted in seconds, but many programming languages and APIs — JavaScript's Date.now() among them — use milliseconds instead. A timestamp that looks unusually large (13 digits instead of 10) is almost always in milliseconds rather than seconds, which this tool detects automatically based on the value's size.