Formula
timestamp (s) = (date − 1970-01-01T00:00:00Z) in secondsmilliseconds = seconds × 1000
- Leap seconds are ignored, as in POSIX time.
Count the seconds elapsed since the Unix epoch.
Worked example
1,700,000,000 seconds
- What do you want to do?
- Timestamp → date and time
- Unix timestamp
- 1,700,000,000
- Unit
- Auto-detect (seconds or milliseconds)
- Time zone
- UTC
UTC date and time
Tue, 14 Nov 2023 22:13:20 UTC
ISO 8601: 2023-11-14T22:13:20.000Z
Relative to now: 2 years ago
Interpreted as: seconds
How it works
A Unix timestamp has no time zone: it identifies one instant, the same everywhere. 1,700,000,000 seconds after the epoch is 22:13:20 UTC on 14 November 2023, which is already the 15th in India. Timestamps of 13 digits are almost always milliseconds (JavaScript's Date.now()), and auto-detect treats values from 100 billion upward that way.
When converting a local date to a timestamp, the tool uses your device's time-zone data and warns if the local time doesn't exist or happens twice because of daylight saving. Negative timestamps are dates before 1970. For calendar-only calculations see Date Calculator: Add or Subtract Time, and to compare times in different cities use the Time Zone Converter.
Assumptions and limits
- “Current” values come from your device clock.