I have a bunch of photos I took with my DSLR. It does not have GPS, so I geo-tagged all the photos using GPS positions I captured on my phone. This part works fine. However, when I upload them to Google Photos, it is saying they were taken in the time zone the GPS coordinates are in, but my camera clock was set to a much different time zone. I suspect this is because it is (wrongly) assuming that the time zone the picture was taken in (the GPS position) is the time zone the clock is in.
At this point, I'm not sure what the easiest way to fix this is. All my photos have multiple places that the timestamp is in, including the file name. And, my image library by convention uses my home time zone for everything, therefore if I were to change the time of the photo to be in a different time zone it would get confusing.