What it does
A Unix timestamp is a count of seconds since 00:00:00 UTC on 1 January 1970. That moment is the Unix epoch. APIs, databases, log files and JSON exports store time this way because one number is easy to sort and does not depend on how a country writes dates.
This page turns that number into a calendar date, and it turns a calendar date back into the number. Use it when a created time, an expiry or a log line is a raw integer and you need the moment it means. Use the other direction when a test, a script or a support note asks for a timestamp and you only have a date and time.
The conversion runs in your browser. The value you enter is not uploaded to NetPivotal, and you do not need an account. It reads one value at a time. For the number of days between two dates, use the date difference calculator linked below.
How to use it
- Choose Timestamp to date or Date to timestamp.
- For a number, paste the timestamp. Leave the unit on Auto if you are unsure, then read the note that says whether seconds or milliseconds were used. Change the unit if that note does not match the system you copied from.
- For a date, use Date and time, or paste an ISO 8601 value that includes a time zone. A UTC example is
2026-08-01T08:49:00Z. The letter Z means UTC. An offset such as +01:00 means local time is that far ahead of UTC. - Read the UTC line first. Then read the line for your computer's time zone. Share the UTC line, or the ISO text, when another person or system needs the same instant.
- Copy or download the summary. It contains the UTC instant, the value in seconds and the value in milliseconds.
An empty field waits for input. A value the tool cannot read produces an explanation, not a guessed date.
A worked example
An access log stores 1785574140. Paste that number and leave the unit on Auto. It has 10 digits, so the tool reads it as seconds.
The UTC result is Saturday, 1 August 2026 at 08:49:00 GMT+0. The ISO form of the same instant is 2026-08-01T08:49:00.000Z. In milliseconds it is 1785574140000.
In London the clock shows 09:49, because August falls in British Summer Time and local time is one hour ahead of UTC. To check the reverse, choose Date to timestamp and paste 2026-08-01T09:49:00+01:00. The seconds come back as 1785574140. If your computer is set to London, you can instead set Date and time to 1 August 2026 at 09:49:00. If your computer uses another time zone, paste the ISO value so the offset is explicit.
The summary you can copy is:
UTC: 2026-08-01T08:49:00.000Z Seconds: 1785574140 Milliseconds: 1785574140000
How the conversion works
Unix time counts seconds from the epoch in UTC. It does not follow your wall clock. Leap seconds, the occasional extra second added to civil time, are left out. Unix, JavaScript and most APIs keep one continuous scale, so a gap of 60 is one minute.
JavaScript stores an instant as a count of milliseconds from the same epoch. This tool converts between that count and seconds. A decimal such as 1785574140.25 means 250 milliseconds past that second. The browser then formats the instant twice, once in UTC and once in the time zone your computer reports. Formatting uses the date tools built into the browser. No request is sent.
Pitfalls and tips
Seconds and milliseconds are easy to swap. 1785574140 and 1785574140000 are the same moment. If you force the shorter number to be milliseconds, the result is Wednesday, 21 January 1970 at 15:59:34.140 GMT+0, not a day in August 2026. Auto mode reads a whole number of 12 digits or more as milliseconds. That starts at 100000000000, which is 3 March 1973 at 09:46:40 UTC. A shorter whole number is read as seconds. A decimal is always treated as seconds. The minus sign is ignored when the digits are counted, so a large negative number can still be milliseconds.
Different languages do not agree on the unit. Date.now() in JavaScript is milliseconds. time.time() in Python is seconds and often includes a fraction. time() in PHP is whole seconds. If you know the language, set the unit yourself and do not rely on Auto.
Time zones cause the other common surprise. 09:49 in London is not 09:49 UTC during British Summer Time. During Greenwich Mean Time the two match. The result shows both lines, with the offset, so you can see which one you have.
The date and time field has no offset of its own. It means that clock time in the time zone of the computer you are using now. On a shared computer, check the time zone before you trust the field. An ISO value with Z or an offset avoids that doubt.
Some local times never happen, and some happen twice. In the UK, clocks jump from 01:00 to 02:00 when British Summer Time starts, so 01:30 does not exist on that morning. The tool rejects a missing time. When clocks go back, 01:30 happens twice. The tool still gives one instant, marks it as repeated, and shows the offset it used. Paste an ISO time with +01:00 or +00:00 when you need a particular one of the two.
Do not paste commas, spaces or scientific notation such as 1.7e9. Copy the digits. Three decimal places is the limit, because that is one millisecond. A leap second, written as second 60, is rejected. A date with no time is rejected too. A bare date is easy to read as midnight UTC, which is still the previous evening in the UK.
Spreadsheets often rewrite a long integer into scientific notation, or they drop the final digits. If a timestamp ends in several zeros and the date is slightly wrong, format the cell as plain text and copy it again.
Some older systems stop at 03:14:07 UTC on 19 January 2038, when a signed count of seconds stored in 32 bits overflows. This converter uses the wider JavaScript range, so later dates still work here. Check the other system before you hand it a timestamp past that point.
The calendar is the Gregorian calendar used by JavaScript, including its leap years. 29 February 2026 is rejected because 2026 is not a leap year. 29 February 2024 is accepted.
Questions people ask
What is a Unix timestamp?
It is the number of seconds since 00:00:00 UTC on 1 January 1970, not counting leap seconds. A millisecond timestamp uses the same starting point and three extra digits.
Why is the result about an hour away from the clock I expected?
The stored number is UTC. In the UK, local time is one hour ahead during British Summer Time and matches UTC during Greenwich Mean Time. Compare the offsets on the two result lines.
Does Auto ever choose the wrong unit?
Yes. A millisecond count from before 3 March 1973 has fewer than 12 digits, so Auto reads it as seconds. A fraction that is not all zeros always means seconds. If the date looks absurd, switch the unit. A result in January 1970 usually means a seconds value was read as milliseconds. A date thousands of years away usually means the opposite.
Is the time I enter sent anywhere?
No. Parsing and formatting happen in this browser. Copy uses the clipboard on your device, and only if you choose Copy result. Download saves a text file on your device in the same way.
Can I use the result for a contract deadline or a bill?
Use the tool to understand a timestamp, then confirm it in the system that owns the deadline. It does not know business days, court rules or invoice terms. For the number of calendar days between two dates, use the date difference calculator. For the length of one shift after a break, use the work hours calculator.
Which dates can I enter?
Typed dates run from the year 0001 to the year 9999, to the millisecond. A number that lands outside the range the browser can format is rejected, rather than rounded to a nearby date.
Related tools
The date difference calculator counts calendar days between two dates. That is a different job from reading a Unix timestamp. The work hours calculator turns a start, a finish and a break into hours for one shift. If the number arrived inside a JSON export, the JSON formatter checks that the text is valid JSON and lays it out so the field is easier to find.