Sometimes I want my Mac OS time to be different from my local time zone. In order to do that I uncheck the box "set time and date automatically" and set the time to whatever I want. This works beautifully for quite some time (days) until randomly something resets the time back to the local timezone. The box with the settings is still unchecked, but clearly some process has set the time automatically to the local one. What is this process & how can I stop it from happening?
I am currently running Mac OS 10.14, but I think this issue also occurred on previous versions of Mac OS. My computer is a Macbook Air in case it matters.
[I also have the box "set time zone automatically using current location" unchecked, but I have manually selected the time-zone I am in.]
Best Answer
You can try blocking outgoing connections to UDP port 123 (NTP) with a PF firewall rule such as:
block drop out quick proto udp from any to any port 123I'm no PF expert, YMMV.
See here for details on how to apply the rule: https://apple.stackexchange.com/a/230556/134740