How to use it
- Type the timestamp or the date-time into Timestamp or date-time.
- Read Read as to see which unit the number was taken to be.
- Pick UTC in A date-time without a zone is in if the date has no time zone and you mean UTC.
- Use Seconds since 1970 and Milliseconds since 1970 in your code, and ISO 8601 (UTC) to compare with a log.
What a Unix timestamp is
A Unix timestamp counts the seconds since 1 January 1970 at 00:00:00 UTC, the Unix epoch, and does not count leap seconds. Many systems count milliseconds instead, and some databases and logs use microseconds or nanoseconds. The same moment has a different number in each unit.
seconds = milliseconds ÷ 1000
milliseconds = microseconds ÷ 1000
microseconds = nanoseconds ÷ 1000How the unit is read
The page does not ask which unit you mean. It counts the digits of a whole number. Up to 10 digits are seconds (until the year 2286), 11 to 13 digits are milliseconds, 14 to 16 are microseconds and 17 to 19 are nanoseconds.
- 1700000000 has 10 digits, so it is seconds.
- 1700000000000 has 13 digits, so it is milliseconds.
- 1700000000000000 has 16 digits, so it is microseconds.
- 1700000000000000000 has 19 digits, so it is nanoseconds.
- Numbers before 1970 are negative, such as -1 for 31 December 1969 at 23:59:59 UTC. POSIX does not define them, but most systems count them back from the epoch, as this page does.
ISO 8601 date-times
A value such as 2023-11-14T22:13:20Z has a date, the letter T and a time. The letter Z means UTC, and an offset such as +03:00 gives the time zone. Without an offset, the page uses the rule you choose in the zone field.
Worked example: 1700000000
The number has 10 digits, so it is read as seconds. It is 14 November 2023 at 22:13:20 UTC, which is 1,700,000,000,000 milliseconds.
The same moment in Istanbul (UTC+03:00) is 15 November 2023 at 01:13:20.
| Input | Read as | Seconds | Milliseconds | ISO 8601 (UTC) |
|---|---|---|---|---|
| 1700000000 | seconds (10 digits) | 1,700,000,000 | 1,700,000,000,000 | 2023-11-14T22:13:20.000Z |
| 2023-11-14T22:13:20Z | ISO 8601 date-time | 1,700,000,000 | 1,700,000,000,000 | 2023-11-14T22:13:20.000Z |
Frequently asked questions
What is the Unix epoch?
The Unix epoch is 1 January 1970 at 00:00:00 UTC. Unix timestamps count the time since then, so a number before that moment is negative.
Why does my timestamp show a date in 1970 or far in the future?
Milliseconds read as seconds land thousands of years ahead, and seconds read as milliseconds land on 20 January 1970. Check the digit count: 10 digits are seconds and 13 are milliseconds.
Is a Unix timestamp the same in every time zone?
Yes. It counts from a fixed instant in UTC, so the number is the same everywhere. Only the local time written next to it depends on your time zone.
Does the page send my dates to a server?
No. The conversion runs in your browser, and it uses the time zone of your own device.
Why does a date with no time zone give another result in a different tool?
A date or date-time without a zone does not name a fixed moment. This page reads it by the rule you choose, while other tools may use UTC or the zone of their server. Choose the rule that matches your data.
Sources
- POSIX: Seconds Since the Epoch (The Open Group)
- RFC 3339: Date and Time on the Internet, timestamps (IETF)
- ECMA-262: Date objects in the ECMAScript specification
Figures and text last checked on Tuesday, November 10, 2026.