Timestamp Converter
Convert Unix seconds, milliseconds or explicit-offset ISO date/time into UTC and a chosen IANA timezone. Compare the same instant without guessing units.
Put the instant in context.
IN YOUR BROWSER / PRIVATE INPUTHow to use the
Timestamp Converter
- 01
Declare the input unit
Select seconds, milliseconds or ISO date/time. An explicit choice prevents a thirteen-digit value from being mistaken for seconds.
- 02
Choose the display zone
Enter an IANA timezone such as UTC, Asia/Karachi or America/New_York. ISO input must include Z or an explicit offset.
- 03
Read all representations
Inspect UTC ISO output, Unix seconds, Unix milliseconds and the selected-zone display. Use current time to start from the actual browser clock.
An instant and its local display are different things
A Unix timestamp represents elapsed time from the epoch in a declared unit. Changing the display timezone does not change that instant. The tool converts the input to a JavaScript Date and then formats it through Intl.DateTimeFormat for the requested zone.
ISO input without a timezone is rejected because a bare local clock value is ambiguous. Invalid calendar dates are checked rather than silently accepting a normalized February overflow. Invalid timezone names produce an error instead of falling back to an unexpected location.
Compare seconds and milliseconds for one instant
The tool’s exact localized wording follows the browser’s timezone data and formatter. Copy the UTC ISO value when an unambiguous machine-readable representation is needed, and include the IANA zone when a human-facing local display matters.
Unix seconds: 1700000000
Unix milliseconds: 1700000000000UTC: 2023-11-14T22:13:20.000Z
Asia/Karachi: 15 November 2023, 03:13:20Check units before diagnosing the date
Unix milliseconds = Unix seconds × 1,000A unit mistake is often much larger than a timezone mistake. The same number interpreted as milliseconds can produce a date near the epoch, while interpreting a millisecond value as seconds can produce a far-future or out-of-range result.
Fractional seconds can represent subsecond time, but JavaScript Date retains millisecond precision. Leap seconds and nanosecond precision are not modeled. The browser clock used by the current-time button is not an independently verified time service.
Keep date conversions unambiguous
Include offset information
Use Z or an explicit numeric offset in ISO input. Do not assume the receiver shares your local timezone.
Use timezone names for human schedules
Named zones can include daylight-saving changes; a fixed offset is not the same as a complete regional timezone rule.
Check the source contract
APIs differ on seconds, milliseconds and allowed precision. Match the documented format rather than guessing from a plausible date.
Timestamp Converter:
questions, answered.
Why does my timestamp show a date near January 1970?
A common cause is treating Unix seconds as milliseconds. Choose the source’s actual unit before comparing timezone displays.
Can I paste an ISO date without Z or an offset?
No. This tool requires explicit offset information so it does not silently interpret an ambiguous local time.
Does choosing another timezone change the Unix timestamp?
No. It changes the displayed clock representation of the same instant.
Does this converter support leap seconds or nanoseconds?
No. It uses JavaScript Date with millisecond precision and its leap-second behavior. Use a suitable specialized time representation when those distinctions matter.
The calculations and checks above describe this tool's implementation. Use these primary references for the underlying formats and publishing guidance.
JavaScript Date ↗ (opens in a new tab)Timezone formatting ↗ (opens in a new tab)Put the instant in context.
Use the controls above, inspect the actual result and keep the source until you are ready to use your new copy.
Use the Timestamp Converter↑