Time Zone on computer keeps switching

Just installed my new T-mobile 5G internet hub.  Excellent connection.  But I just noticed that my computer that is wired into my switch keeps changing time zones.  I am in the Pacific Standard time zone and it switches to mountain standard time.  It goes back and forth like this all day.

I tried to manually set my time zone but I cannot.  It is “grayed out”.

Anyone having the same issue?

Thanks for your help.