# Documentation

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# posixtime

Convert MATLAB datetime to POSIX time

## Syntax

``p = posixtime(t)``

## Description

example

````p = posixtime(t)` returns POSIX® times equivalent to the `datetime` values in `t`. The POSIX time is the number of seconds (including fractional seconds) elapsed since 00:00:00 1-Jan-1970 UTC (Universal Coordinated Time), ignoring leap seconds. `p` is a `double` array.If the time zone of `t` is not specified, then `posixtime` treats the times in `t` as UTC times. This interpretation might differ from your treatment of “unzoned” `datetime` arrays in other contexts. For example, you might think of `datetime('now')` as returning your local time. However, `posixtime` interprets it as a UTC time.If the time zone of `t` is specified, then `posixtime` uses the offset for the time zone to compute POSIX times with respect to UTC.The best practice is to specify the time zone of `t` before calling `posixtime`.```

## Examples

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Create `datetime` values and convert them to the equivalent POSIX® times. Show the differences in POSIX times between zoned and unzoned `datetime` values. The best practice is to specify a time zone for a `datetime` array before calling `posixtime`.

Create a `datetime` array and specify its time zone.

```t1 = datetime('2016-07-29 10:05:24') + calmonths(1:3); t1.TimeZone = 'America/New_York'```
```t1 = 1x3 datetime array 29-Aug-2016 10:05:24 29-Sep-2016 10:05:24 29-Oct-2016 10:05:24 ```

Convert `t1` to the equivalent POSIX times. `posixtime` accounts for the time zone offset when it computes POSIX times.

```format longG p1 = posixtime(t1)```
```p1 = 1472479524 1475157924 1477749924 ```

Create a `datetime` array with the same values as `t1`, but with no time zone. Convert it to the equivalent POSIX times. `posixtime` treats the times in `t2` as UTC times, with no time zone offset.

```t2 = datetime('2016-07-29 10:05:24') + calmonths(1:3); p2 = posixtime(t2)```
```p2 = 1472465124 1475143524 1477735524 ```

Show the differences between `p2` and `p1`. The differences are equal to the time offset, in seconds, between UTC and the time zone of `t1`.

`p2 - p1`
```ans = -14400 -14400 -14400 ```

## Input Arguments

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Input date and time, specified as a `datetime` array.