Unix Timestamp Converter
Convert a Unix timestamp in seconds or milliseconds to a UTC date and time, or a UTC date and time back to a Unix timestamp.
Result
ISO 8601 date and time (UTC): 2023-11-14T22:13:20Z
All times are UTC. Unix time counts every day as exactly 86,400 seconds, so leap seconds do not appear in it.
- Timestamp in seconds
- 1700000000
- Timestamp in milliseconds
- 1700000000000
- Date (UTC)
- November 14, 2023
- Time (UTC)
- 22:13:20
https://calcgallery.com/notation-conversions/unix-timestamp-converter-calculator/
Unit conversions follow from exact definitions and published notation rules. Sizes follow published standards and are approximate: makers grade their own, so check their chart. Figures are rounded only for display. Read the full disclaimer
How to use the Unix Timestamp Converter
- To read a timestamp, paste it in and say whether it counts seconds or milliseconds. Ten digits is usually seconds; thirteen is usually milliseconds.
- To make a timestamp, choose date and time to timestamp and enter the moment in UTC.
- Read the result as an ISO 8601 date and time, as a date and a 24-hour time, and as a timestamp in both seconds and milliseconds.
Counting seconds from the epoch
POSIX, the standard behind Unix-like systems, defines the timestamp by formula from a UTC date and time. The key sentence is that every day is accounted for by exactly 86,400 seconds, which turns the conversion into plain calendar arithmetic:
timestamp = days since 1970-01-01 × 86,400 + seconds into the daydays = floor(timestamp ÷ 86,400)time of day = timestamp − days × 86,400The page counts the days with the proleptic Gregorian calendar, the same one the date calculators use, and does not ask your computer for the time. It converts only what you type, so the result is the same on every device.
Seconds or milliseconds
JavaScript, Java and many web APIs count milliseconds rather than seconds. A millisecond timestamp is a thousand times larger, so reading one as seconds lands tens of thousands of years in the future. The page asks which you have rather than guessing from the number of digits. If a 13-digit timestamp is read as seconds, it falls outside the years the page can show, and the page says it looks like milliseconds instead of giving a date. Before 1970 the page takes the whole second at or before the moment and counts the milliseconds forward from it, which is why −1 millisecond is 23:59:59.999 on 31 December 1969.
ISO 8601 output
The main result is written the way ISO 8601 writes a UTC moment: date, the letter T, time, and a Z for UTC. It sorts correctly as text and is widely understood by software, so it is a safe form to copy into another system.
With your numbers
- 19,675 whole days × 86,400 s + 80,000 s into the day
- Day 19,675, counting 1 January 1970 as day 0, is November 14, 2023, 22:13:20 UTC
- ISO 8601 = 2023-11-14T22:13:20Z
Quick reference
All times are UTC. Unix time counts every day as exactly 86,400 seconds, so leap seconds do not appear in it.
| Example | Result |
|---|---|
| 1700000000 | ISO 8601 date and time (UTC): 2023-11-14T22:13:20Z |
| 0, the epoch | ISO 8601 date and time (UTC): 1970-01-01T00:00:00Z |
| 2147483647, the 32-bit limit | ISO 8601 date and time (UTC): 2038-01-19T03:14:07Z |
| −1, one second before | ISO 8601 date and time (UTC): 1969-12-31T23:59:59Z |
| 1700000000123 milliseconds | ISO 8601 date and time (UTC): 2023-11-14T22:13:20.123Z |
| 1 January 2000, 00:00 UTC | Timestamp in seconds: 946684800 |
| 20 July 1969, 20:17:40 UTC | Timestamp in seconds: -14182940 |
| 25 September 2026, 12:34:56 UTC | Timestamp in seconds: 1790339696 |
Common questions about the Unix Timestamp Converter
- What is a Unix timestamp?
- The number of seconds since 00:00:00 UTC on 1 January 1970, the moment known as the epoch. It is how many operating systems, databases and programming languages store a point in time, because a single integer is easy to sort, compare and subtract.
- Does Unix time count leap seconds?
- No. The POSIX standard defines every day as exactly 86,400 seconds. When a leap second is added to UTC, Unix time does not gain a second, so the difference between two timestamps falls short of the true elapsed time by the number of leap seconds inserted between them.
- Why does my timestamp show the wrong hour?
- Timestamps are in UTC, and this page shows UTC. Your own clock is UTC plus or minus your offset, and that offset changes with daylight saving. Use the time zone converter to see the same moment in a named city.
- What happens in 2038?
- A signed 32-bit integer can hold up to 2,147,483,647, which is 03:14:07 UTC on 19 January 2038. Software that still stores time in 32 bits will wrap around to a date in 1901 one second later. Software that stores time in 64 bits is unaffected.
- Can a timestamp be negative?
- Yes. A negative timestamp counts back from the epoch, so −1 is the last second of 1969. The page handles any moment from the year 1 to the year 9999.