If you run MATLAB on macOS High Sierra (version 10.13) or later, and you create a datetime array and specify its time zone as 'local', then it might throw errors or warnings that refer to the system time zone setting. These errors or warnings can occur even when the system time zone is set correctly. You might see an error message similar to:
Error using datetime (line 522)
The system time zone setting, 'local', is not valid. See the datetime.TimeZone property for details about specifying time zones.
Or a warning message similar to:
Warning: The system time zone setting, 'US/Eastern', does not specify a single time zone unambiguously.
It will be treated as 'America/New_York'. See the datetime.TimeZone property for details about specifying time zones.
when your system's time zone is not set to 'US/Eastern'. Also, if you use the PARPOOL command, it might throw an error or warning such as those shown above. The Parallel Computing Toolbox uses the datetime class during initialization.