Date & Time Converter
Convert Unix timestamps to human-readable dates, format dates as ISO 8601, or convert times between time zones.
"Now" button:
How to Use
- Choose a mode: "Unix Timestamp", "ISO 8601 Format", or "Time Zone".
- Unix Timestamp: enter a timestamp to convert it to a readable date, or pick a date/time to get its Unix timestamp (in both seconds and milliseconds).
- ISO 8601: pick a date and time to see it formatted as a standard ISO 8601 string, in both UTC and your local time zone.
- Time Zone: enter a date/time and source time zone, then select a target time zone to see the converted time.
- Results update instantly as you type — no need to click Calculate.
When to Use This
- Debugging a log line that stores times as integers, where the seconds and milliseconds toggle settles which unit the field is using.
- Writing an API payload that requires an ISO 8601 string, with both the UTC form and the offset-carrying local form shown together.
- Scheduling a call across offices by converting a wall-clock time from one zone into another before you send the invitation.
- Checking what a database timestamp means in your own local time, including the relative phrase telling you whether it is past or future.
Frequently Asked Questions
About This Calculator
A Unix timestamp counts seconds since 1 January 1970 UTC, ignoring leap seconds, and it names an instant rather than a wall-clock reading. An ISO 8601 string names the same instant but carries an offset, which is why 14:30Z and 20:00+05:30 are the same moment. Confusing an instant with a local reading is the usual source of off-by-hours bugs in logs and APIs.
Three modes share the page. Unix mode reads a number as either seconds or milliseconds, depending on the toggle, and returns a UTC string, a full local rendering, a relative phrase and an ISO string, and it converts back from a date and time you pick. ISO mode prints the UTC form and a local form carrying your browser's offset. Time zone mode uses Intl.DateTimeFormat to read each zone's offset at the relevant instant.
Notes & Limits
- The relative phrase approximates a month as 30 days and a year as 365, so two months ago is a rough label rather than a calendar count.
- Time zone mode resolves the source offset at the entered time read as UTC, so a time inside the hour of a daylight-saving shift can come out an hour off.
- The zone menu lists 24 common IANA zones plus your browser's own; other zones cannot be typed in and no historical zone picker is offered.
- ISO mode and the reverse Unix conversion read your entry in the browser's local zone, not UTC, so a machine set to the wrong zone gives the wrong instant.