Every API response, database row and log line seems to include a number like 1754640000. That's a Unix timestamp — the seconds since January 1, 1970, UTC. This guide explains what timestamps are, the classic seconds/milliseconds trap, and how to convert them to human-readable dates (and back) without guessing.
What Is a Unix Timestamp?
A Unix timestamp counts seconds (or milliseconds) since the Unix epoch: 1970-01-01 00:00:00 UTC. Because it's defined in UTC, the same timestamp means the same instant everywhere — only the displayed local time differs. That's why timestamps are the safest way to store times across time zones.
The Seconds vs. Milliseconds Trap
JavaScript and many databases use milliseconds (13 digits), while most Unix tools and APIs use seconds (10 digits). Get them mixed up and your date is off by a factor of 1000 — roughly 11.6 days for every second of error. A quick rule of thumb:
- 10 digits ≈ seconds (e.g.
1754640000= 2025-08-08) - 13 digits ≈ milliseconds (e.g.
1754640000000= the same instant)
Auto-detection by digit count is exactly what the converter does when you don't specify the unit.
Local Time vs. UTC
A timestamp converts to the same instant but a different wall-clock time per time zone: 1754640000 is 2025-08-08 12:00 UTC and 2025-08-08 20:00 in UTC+8. Converters show both views — UTC and your local time — so you can read either.
How to Convert Timestamps Online
- Open the tool: go to the timestamp converter.
- Paste the timestamp: seconds or milliseconds — auto-detected by length, or choose the unit manually.
- Read the date: see UTC and your local time, plus the weekday.
- Go the other way: pick a date and time to get its timestamp in seconds and milliseconds.
- Use the live clock: the current timestamp is always displayed for reference.
Tip: when debugging an API, confirm which unit the docs specify. If you see a date 11.6 days off, you've almost certainly mixed seconds and milliseconds.
Frequently Asked Questions
What is the current Unix timestamp?
The converter shows it live. At any moment it's the seconds elapsed since 1970-01-01 UTC — currently around 1.78 billion and counting.
Why is my timestamp converting to the wrong date?
Almost always a seconds/milliseconds mismatch. If the date looks about 11.6 days off per unit, multiply or divide by 1000.
Is 1970-01-01 significant?
It's the Unix epoch — a convention, not a calendar event. Negative timestamps represent dates before 1970 and are valid too.
Is my timestamp uploaded when I convert it?
No. The timestamp converter computes locally in your browser.
References
- Unix time — Wikipedia: https://en.wikipedia.org/wiki/Unix_time
- Date and time handling — MDN Web Docs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date