One of my mistakes on my trip to Yosemite was that, after a few days, I noticed that my photo files were dated for one day (e.g. Sept 12th) and I knew I had taken them the the previous day. What was wrong?
I had forgotten to change the time zone on the cameras.
So, for the first few days I need to deduct 8 hours if I need to know the time of day at which I captured the photo.
Now I need to remember to change them back when I get home!