It has everything to do with the time zone changing. I never noticed before, but I just went back and checked some of my photos and see that the time was adjusted for my home time zone after my return. I probably never noticed because I watermark my photos with the date and time stamp, which remains correct. You can edit the date/time on your pictures after the fact, or you can add the watermark, as I do. I do not see a setting in either camera settings or gallery settings to prevent this (I know the calendar has a setting to keep my home time zone, so appointments don't get shifted). However, I did also notice that in the Google photos backup, the date and time match the watermark. So, apparently, only Gallery makes this change. Actually, One drive also makes a change, but it keeps the original date/time it just shows date/time taken (correct) and date modified (new time zone adjusted time)
