How to use the Unix timestamp calculator
Pick a conversion direction, enter the value, and choose the time zone that gives the reading its meaning. The result shows the UTC value, the selected local value, the formula, and the assumptions used for the calculation.
- Select Timestamp → Date or Date → Timestamp.
- Enter a Timestamp and choose its Unit, or enter a Date and Time (24-hour).
- Choose Show local time in or Interpreted as local time in.
- Click Calculate, then use Copy result or Download result (.txt) for the text output.
Convert a timestamp to a date
Choose Timestamp → Date when you have an epoch number. Select Seconds since epoch or Milliseconds since epoch, then choose Show local time in. The calculator keeps that instant and displays it in the selected zone alongside UTC.
Timestamp: 1700000000
Unit: Seconds since epoch
Show local time in: UTC
UTC (ISO 8601): 2023-11-14T22:13:20ZA Unix timestamp identifies an instant relative to 1970-01-01T00:00:00Z. Changing Show local time in changes the displayed clock reading while the timestamp stays the same.
Convert a date to a Unix timestamp
Choose Date → Timestamp when you have a calendar reading. Enter Date and Time (24-hour), then select the zone in Interpreted as local time in. The result gives seconds and milliseconds since the epoch. The calculation uses Math.round(); the time field accepts HH:MM or HH:MM:SS.
Unix timestamp time zones and input limits
- The zone selectors use values exposed by your browser's
Intlimplementation. A fixed fallback list is used when zone enumeration is unavailable. - Your browser's detected zone is selected when the page loads. Use current time fills the timestamp, date, and time inputs, then waits for Calculate.
- A blank Time (24-hour) field becomes
00:00:00. Invalid dates, malformed numbers, unsupported zones, and timestamps outside JavaScript'sDaterange show an error. - Leap seconds are ignored, so each day has 86,400 seconds. The calculator does not report daylight-saving gaps or overlaps; it resolves those local readings with a heuristic offset.
Where this conversion comes up
For a log entry, convert the epoch value to a readable time and check the selected zone against the UTC value before copying the result.
For a scheduled local reading, select its zone and convert the Date and Time (24-hour) fields into seconds and milliseconds.
When a timestamp has an unclear unit, run it once with Seconds since epoch and again with Milliseconds since epoch, then compare the displayed dates.
Choose the right date and time calculator
Use the Date and Time Calculators category when you need a different kind of date math. The Time Zone Difference Calculator compares the offset between two IANA zones at a chosen date and time. The Date Add Calculator adds or subtracts calendar units from a date. The Countdown Calculator calculates time remaining until, or elapsed since, a target date and time.
Frequently asked questions
How do I convert a Unix timestamp to a date?
Select Timestamp → Date, enter the number, choose its Unit, select Show local time in, and click Calculate. The result includes the selected local time and UTC.
How do I convert a date to a Unix timestamp?
Select Date → Timestamp, enter Date and Time (24-hour), choose the zone in Interpreted as local time in, and click Calculate. The result shows seconds and milliseconds.
Does a Unix timestamp include a time zone?
No. It identifies one instant relative to UTC. The zone selector controls the displayed date or the interpretation of an entered local clock reading.
Does the Unix timestamp calculator use an external time service?
No. The conversion uses the entered values and time-zone data supplied by your browser's Intl implementation. The script makes no request to an external time service.