This is because twenty-four latitude lines were chosen so that 24 hours represents a 360 revolution around the planet. As earth spins on its axis, different places receive sunlight at different times. Each day goes from morning to night as earth turns because the earth spins from west to east therefore the day moves from east to west. Lines of longitude help us keep track of time differences from place to place. Mapmakers divided earths 360 degrees of longitude by 24 hours which results to 15, the time changes by one hour every 15 degrees. It is one hour earlier every 15 degrees of longitude to the west and it is one hour later every 15 degrees of longitude to the east.
