The Islamic prayers are fixed at the same "time" period each day -- before dawn, noon, afternoon, sunset, and evening. Because of the rotation of the earth, the revolution of the earth around the sun, the tilt of the earth, the various latitudes of the earth's locations, daylight savings time, etc. -- the "times" (according to the clock) for these prayers do change from day to day and depend on location. Islamic prayer times were traditionally set according to the movement of the sun, not of the clock, and this is how they continue to be observed.