Millisecond Timestamp Converter
A millisecond timestamp is a Unix timestamp multiplied by 1,000 — it counts milliseconds instead of seconds since January 1, 1970 UTC. You can identify a millisecond timestamp by its 13-digit length (e.g. 1700000000000), compared to the 10-digit seconds format (e.g. 1700000000). This converter automatically detects which format you have and applies the correct conversion.
JavaScript is the most common source of millisecond timestamps. The Date.now() method and new Date().getTime() both return milliseconds. Java's System.currentTimeMillis() also returns milliseconds. This makes 13-digit timestamps extremely common in web applications, mobile apps, and any system that uses JavaScript on the frontend or Java on the backend.
Seconds vs milliseconds: common confusion
The most frequent timestamp error in software development is treating a millisecond timestamp as seconds or vice versa. If you see a date in 1970 when you expected a recent date, you have a millisecond timestamp being parsed as seconds. If you see a date far in the future (like 2527), you have a seconds timestamp being parsed as milliseconds. The fix is always to either multiply or divide by 1000.
Millisecond timestamps in code
JavaScript — current timestamp in ms: Date.now()
JavaScript — ms to Date: new Date(1700000000000) (no multiplication needed for ms)
Python — ms timestamp: int(time.time() * 1000)
Java — ms timestamp: System.currentTimeMillis()
Convert ms to seconds: divide by 1000 (integer division)