I am located in Sofia, Bulgaria. Bulgaria has only one time zone and official time in Bulgaria is UTC+3. In Bulgaria there are summer and winter times, winter is consider default. When it goes to it, it goes to UTC+2. I am not sure if they (government) still keep changing that or it has been made obsolete. In your system there are two time zones, in which Sofia falls: the first is GMT +1:00 Sarajevo; Skopje; Sofia; Vilnius; Warsaw; Zagreb; and the second is GTM +2:00 Helsinki; Riga; Tallinn; Kyiv; Sofia; Vilnius; I set several times the first one, GMT +1:00, and in some period of time it goes to the second one, GMT +2:00. So I have notice this change and started to wonder why it happens. That's it. I believe it is not a security issue. I do not use shared machine and I believe nobody hacked one of mines. Account is old, from 2007 and during this period I have changed several machines, for sure I have logged from many places. I clear user data quite often and I also disconnect all existing connections, if any, expect the current one. However, I am not 100% sure, after all I buy a retail Windows 10 OS and I am sure there is a backdoor in it, but I guess only government security employees can access it and I don't see a reason for them to do it.