>I selected timezone "GMT-4", but I am seeing the time as if I had selected "GMT-3". It used to work correctly. We don't use daylight saving time in Bolivia, so there should be no need for me to do regular adjustments here.

As mentioned in the doc, some members may have to change it once every six months in their account setup as we do not go dynamically for that. There are specific reasons to do it like that. So, once per six months, in your case, it's a small step to do. :)