Digital cameras record the exact time each photo was taken. HoudahGeo relies on this information to match photos to a GPS tracklog. Unfortunately, most digital cameras fail to specify which time zone the recorded time is expressed in. I.e for a photo taken at noon, HoudahGeo cannot tell if it was noon in Los Angeles, or in Luxembourg, etc.
HoudahGeo thus needs a little help to make sense of the camera timestamps. Getting camera clock setup right is essential for automatic geocoding to work.