Timestamp in seconds
t = (instant − 1970-01-01T00:00:00Z) in seconds
Convert a Unix timestamp to a date (and a date to a timestamp)
Turn a Unix timestamp into a local date and an ISO 8601 UTC date, or a date and time into a timestamp, with automatic detection of seconds and milliseconds.
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How does this tool work?
A Unix timestamp, or epoch time, is the number of seconds elapsed since 1 January 1970 at 00:00 UTC. It is how databases, server logs, APIs and authentication tokens record an instant, with no time zone and no date format. This converter turns a timestamp into a readable date and time, in your time zone and in UTC as ISO 8601, and also works the other way round: it gives the timestamp of a date and time you enter. It recognises millisecond timestamps, used by JavaScript and many APIs, on its own.
A timestamp counts the seconds since the Unix epoch, 1970-01-01T00:00:00Z. POSIX counts every day as exactly 86,400 seconds: leap seconds are ignored, which is why a timestamp converts to a date with plain arithmetic.
Enter a number: from 100,000,000,000 (12 digits) upwards it is read as milliseconds, below that as seconds. The unit used is shown next to the field. The date appears in your device’s time zone, and the exact instant in UTC as ISO 8601.
The other way round, the date and time you enter are interpreted in your device’s time zone, then converted to whole seconds, or to milliseconds if you have just converted a millisecond timestamp.
Negative timestamps are instants before 1970. The supported range is that of JavaScript dates: ±8.64 × 10¹⁵ milliseconds, roughly 270,000 years on either side of 1970.
How to use this tool
Enter a timestamp or a date
Paste a timestamp in its field, or pick a date and time; the other field updates.
Check the detected unit
Seconds or milliseconds appear next to the timestamp.
Read the UTC instant
The ISO 8601 line ends in Z: it is UTC, with no time-zone ambiguity.
Use Now or share
The button inserts the current timestamp; the calculation link keeps the timestamp you entered.
From timestamp to date
A timestamp is a distance in seconds from the Unix epoch; the date follows from 86,400-second days.
Days and remainder
days = ⌊t / 86400⌋; seconds of day = t − 86400 × days
Days are counted from 1 January 1970, in UTC.
Milliseconds
t(ms) = 1000 × t(s)
- t
- Unix timestamp in seconds
- 86400
- seconds in a POSIX day (24 × 60 × 60)
Use cases
Reading a log or a database
Turn a created_at column or a log line into a readable date.
Debugging an API or a token
Check the exp, iat or nbf claims of a JWT, or a date returned by an API, in seconds or milliseconds.
Preparing a query
Get the timestamp of an exact date to filter records or schedule a job.
Comparing local time and UTC
See the local and UTC time of the same instant at a glance, handy for a team spread across time zones.
Examples
A 10-digit timestamp
That is 14 November 2023 at 17:13:20 in New York (UTC−5 in winter). 1,700,000,000 ÷ 86,400 = 19,675 whole days after 1 January 1970, plus 80,000 s, i.e. 22 h 13 min 20 s.
Input
1700000000Result
2023-11-14T22:13:20.000ZThe same instant in milliseconds
With 13 digits the number is read as milliseconds, giving the same result.
Input
1700000000000Result
2023-11-14T22:13:20.000ZThe year 2038 problem
This is the largest signed 32-bit integer. A system that stores timestamps in 32 bits overflows one second later.
Input
2147483647Result
2038-01-19T03:14:07.000ZBefore 1970
A negative timestamp counts back from the epoch: −86,400 s is one day earlier.
Input
-86400Result
1969-12-31T00:00:00.000ZTips and best practices
- 10 digits: seconds (until the year 2286); 13 digits: milliseconds. A millisecond timestamp from before March 1973 has fewer than 12 digits and would be read as seconds.
- A timestamp holds no time zone: it is always a UTC instant. Only its display depends on the zone.
- The swap button only changes the order of the fields; conversion works in both directions at any time.
- To display a date in another time zone than yours, use the time zone converter.
- A timestamp in seconds drops the milliseconds: 12:00:00.999 gives the same value as 12:00:00.
Sources and references
- The Open Group, IEEE, POSIX.1-2024 — Base Definitions, 4.19 Seconds Since the Epoch (opens in a new tab), The Open Group Base Specifications Issue 8, 2024Page in English
- MDN Web Docs, Date — JavaScript reference (opens in a new tab), MozillaPage in English
- G. Klyne, C. Newman, RFC 3339 — Date and Time on the Internet: Timestamps (opens in a new tab), RFC Editor, 2002Page in English
- ISO — ISO 8601 date and time format (opens in a new tab)Page in English
Frequently asked questions
What is a Unix timestamp?
The number of seconds since 1 January 1970 at 00:00:00 UTC, known as the Unix epoch. It is defined by the POSIX standard and used by most computer systems.
How can I tell whether a timestamp is in seconds or milliseconds?
Count the digits: today, 10 for seconds and 13 for milliseconds. The tool treats any number of at least 100,000,000,000 as milliseconds.
Does a Unix timestamp include leap seconds?
No. POSIX counts every day as 86,400 seconds, and JavaScript also ignores leap seconds. That is what makes an exact conversion by arithmetic possible.
Why does the displayed time differ from UTC?
The date field uses your device’s time zone, including daylight saving time. The ISO 8601 line gives the same instant in UTC.
What is the year 2038 problem?
Systems that store timestamps in a signed 32-bit integer cannot go past 2,147,483,647, which is 19 January 2038 at 03:14:07 UTC. 64-bit systems are not affected.
Can I convert a date before 1970?
Yes. The timestamp becomes negative: 31 December 1969 at 00:00 UTC is −86,400.
What happens with a local time skipped by a clock change?
When clocks go forward, a local time such as 2:30 does not exist. The browser shifts it; check the UTC line to see which instant was actually used.
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