Matlab Unix Time to Datetime

Unix time is a way of representing time as a number of seconds that have elapsed since January 1st, 1970 at 00:00:00 UTC. In Matlab, Unix time can be converted to a datetime object using the built-in datetime function.

Unix Time Conversion Function

Below is a Matlab function that takes a Unix time value as an input and returns a datetime object:

function dt = unixTimeToDatetime(unixTime)
% Convert Unix time to Matlab datetime object
secondsSinceEpoch = unixTime - 719529*24*60*60; % Adjust for Matlab epoch
dt = datetime(secondsSinceEpoch, 'ConvertFrom', 'posixtime', 'TimeZone', 'UTC');
end

Usage

Simply pass a Unix time value to the unixTimeToDatetime function to receive a datetime object:

>> unixTimeToDatetime(1625674685)
ans =
  datetime
   2021-07-07 14:04:45

How it Works

The formula used to convert Unix time to Matlab time is as follows:

secondsSinceEpoch = unixTime - 719529*24*60*60;

The 719529*24*60*60 value represents the number of seconds between January 1st, 0000 at 00:00:00 and January 1st, 1970 at 00:00:00 UTC. By subtracting this value from the Unix time value, we are essentially aligning the Unix epoch (January 1st, 1970 at 00:00:00 UTC) with the Matlab epoch (January 1st, 0000 at 00:00:00).

Once the Unix time value has been adjusted, it can be passed to the datetime function using the 'ConvertFrom', 'posixtime' option, which tells Matlab that the input value is a Unix time value (which is the same as a POSIX time value). The 'TimeZone', 'UTC' option is used to ensure that the datetime object is created in UTC time.

Conclusion

Converting Unix time to a datetime object in Matlab is a simple process that involves adjusting for the difference between the Unix epoch and the Matlab epoch, and passing the adjusted value to the datetime function with appropriate options.