What I want to achieve is this:
we are using SharePoint 2013 and I want to set my timezone and have all SharePoint sites respect this.
I am a bit confused because there are several places where one could set a timezone.
The Web-App (?)
https://<mysite url>/_layouts/15/EditProfile.aspx?UserSettingsProvider=<ID here>
I changed the timezone on my site (3) in my profile but that does not have any effect on any SP site. I still see all dates/times in the timezone that has been configured for the site. When I try to change it on site or web level I get an error message whilst trying to save my changes to the profile there (this site has not been shared with you).
I found a good explanation of the problem that I have with a fixed timezone on a SP site for all visitors: