We could solve it if we knew the orientation of the buoy. I'd suspect it's facing the open ocean, probably to the northwest, which, if I see the position of the Sun right, would place us to Alaskan time.
Other possibility: Daily temperature maximum, if the time in the table is the same as the time in the camera footprint. Looks like sometimes a mild maximum after 12 and a sharp spike around 22 hours. In my trivial mind the first could be daily max, the second would then be sunlight in the buoy sensors...