Some times in the movie, the day turn to night or the night become day in the same scene. Like in the gravedigger scene, they are talking during the day, then it's dark .
Watch "Ed Wood", Tim Burtons fantastic biopic of 'the worst director of all time'. You will see a whole load of instances when Wood made stupid mistakes in his movies, and I think most of them are true.
Day and night changes are common in Ed Wood's films. It's partly due to his weak grasp of technology in filmmaking and partly due to the use of a technique called "Day For Night". Many older films actually film the outdoor "night" scenes during the day and underexpose the film to appear dark. This was due to the lack of good motion picture film for low light scenes. One way to tell if a night scene was shot during the day is to watch for shadows being cast by the actors and objects. In Ed Wood's case, he probably just forgot to adjust the F-stop while shooting some of the night scenes so they don't match up.