How to change the time zone in Firefox in Mac os High Sierra?

Question

VPN

I use VPN, in order to surf without impersonating myself, the system time must match the time of the country of the VPN server. I always check through whoer.net that the times don't differ. I updated the Mac system and, as you guessed, it all became f * opu why the hell can I not change UTC to GMT, there is an error in the terminal, but there are no these changes in Firefox.
In short, you need whoer.net through firefox to see my system time and the Netherlands in the same way .... Maybe he knows how to fix this nonsense all day I fight
PS
In the time and date settings, I climbed everything set as it should, it does not help
sudo ln -sf /usr/share/ zoneinfo/UTC /etc/localtime in the terminal does not help or I somehow incorrectly use it