Today I decided to change the times that several of my lamps would turn on from a fixed time each day to a time based upon Sunset. After I changed the scene trigger times to about an hour before sunset, and saved the information, I went to the scene panel only to find that the time for the next event on all of the changed schedules - was about 1:xx PM in the afternoon - 5 hours too early! After some scrambling and thinking, I went to the settings tab, and pressed on Location (UI7). And I saw that even though my state information was filled in correctly, both the latitude and longitude boxes were empty. After having Vera re-locate my current position the boxes filled in correctly and when I went back to the scene panel the times for the next event were now correct.
If any of you are having a problem with an event triggering at the wrong time, when sunrise/sunset is used as a trigger, you may want make sure that all of the information about your location is filled in and correct.