MacBook time zone setting dimmed, cannot be changed by administrator

You have to first turn off the setting "Set time zone automatically using your current location", then you should be able to manually adjust the time zone.

If you want to have the time & time zone adjusted automatically, then you need to give macOS permission to use your location. You can check in the "Privacy & Security" System Settings. Near the top of the right pane, you will see an item called "Location Services" which will have a number and a ">" symbol. Click that line which will open up another section.....near the bottom of the list is a line "System Services" with a button called "Details....". You will find an option to enable "Setting time zone" which must be turned on for automatic setting of the date & time and time zone. At least this is where the options are for macOS 26.x Tahoe.

Hi,

Try to use Terminal command;

sudo systemsetup -settimezone