Complex sentence: The day, which starts at sunrise and ends at sunset, is divided into four "prahara" s of equal length; and, the night, which starts at sunset and ends at sunrise, is also divided into four equal watches.
Split into simpler sentences: The day, which starts at sunrise and ends at sunset, is divided into four "prahara" s of equal length. Similarly, the night, which starts at sunset and ends at sunrise, is divided into four equal watches.