Unix Timestamp Converter
Staring at a 10-digit number from an API log and wondering what date it is? This free unix timestamp converter translates epoch time to a human-readable date — or does the reverse, turning any date and time into its Unix timestamp. It shows the result in UTC and in your browser's local time zone, and auto-detects whether your input is in seconds or milliseconds.
Enter your value
Your results
Enter a timestamp or pick a date to see the conversion.
How to use this calculator
Pick a direction at the top. In Timestamp → date mode, paste any Unix timestamp into the field — it works with both seconds (10 digits, e.g. 1790035200) and milliseconds (13 digits, e.g. 1790035200000). The unit is detected automatically by the size of the number, so you never have to guess.
In Date → timestamp mode, choose a date and time with the picker. The input is interpreted in your browser's local time zone, and the calculator instantly returns the matching Unix timestamp in both seconds and milliseconds.
Results update the moment you type or change an input — the Calculate button re-runs the conversion at any time. If you enter something that isn't numeric or is outside the representable date range, you'll see an error message instead of a wrong answer.
How it works
A Unix timestamp counts the seconds since 1970-01-01T00:00:00Z, a reference moment called the Unix epoch. Converting is plain arithmetic: to go from timestamp to date, multiply seconds by 1,000 to get milliseconds and construct a calendar date from that millisecond count; to go the other way, take the millisecond count of a date and divide by 1,000 (rounding down).
Seconds vs milliseconds is the most common source of confusion. Most backends, databases, and APIs store epoch time in seconds (10 digits today), while JavaScript's Date object uses milliseconds (13 digits). A current-magnitude value is unambiguously one or the other, which is why this tool detects the unit by magnitude: any absolute value of 100,000,000,000 or more is treated as milliseconds, anything smaller as seconds.
The timestamp itself is time-zone independent — the same number means the same instant everywhere on Earth. For display, the calculator renders it two ways: as UTC (ISO 8601 and UTC date+time, identical for everyone) and in your browser's local time zone, so you can see what the instant means where you are.
All math runs in your browser — nothing you enter is sent anywhere. Range is limited to what JavaScript dates can represent (about ±8.64×1015 milliseconds); out-of-range values are rejected with an error.
Frequently asked questions
What is a Unix timestamp?
A Unix timestamp (also called epoch time) is the number of seconds that have elapsed since 1970-01-01T00:00:00Z, a moment known as the Unix epoch. For example, 1790035200 seconds after the epoch is 2026-09-22T00:00:00Z. Timestamps are time-zone independent: the same timestamp always refers to the same instant everywhere on Earth.
Seconds vs milliseconds — how do I tell them apart?
Count the digits. A current Unix timestamp in seconds has 10 digits (e.g. 1790035200); in milliseconds it has 13 digits (e.g. 1790035200000). JavaScript's Date object uses milliseconds, while most APIs and databases use seconds. This converter auto-detects the unit by magnitude: values of 100,000,000,000 or more are treated as milliseconds, smaller values as seconds.
What time zone does the converter use?
The converter always shows the UTC (Coordinated Universal Time) result — the same instant, rendered in a time-zone-neutral way — plus the equivalent date and time in your browser's local time zone. The Unix timestamp itself is identical in every time zone, so converting in either direction is unambiguous.
What are the minimum and maximum supported dates?
The converter handles any timestamp JavaScript can represent: roughly ±8,640,000,000,000,000 milliseconds, covering dates from about 271,821 BCE to 275,760 CE. Values outside that range are rejected with an error. Note that old 32-bit systems and software only support signed 32-bit timestamps, which overflow on January 19, 2038 — the so-called Year 2038 problem.