The earthquake actually occurred at 5:13 am. In the movie the timing appears to be in the late evening, not in the early morning. The prologue of the opening credits states the correct time of the earthquake: April 18, 1906 at 5:13 am but it is easy to understand any confusion since with the cinematography at the time, day for night shots were used in exterior sets and with model sets, so that the full impact of the earthquake in progress could be easily seen. Also, it took at least three days for the fire to be extinguished and with the one night shot in those sequences, it appears that the timing of events after the earthquake was much shorter than it actually was.