These ever recurring changes repeat with each yearly orbit. Day after day it is the same, but not quite. Each wave of daylight comes at a slightly different place upon our horizon. Nights are as short as they can get. Then, slowly, as Earth moves on, the Sun slips southward in its rising and setting points and lower across the sky each day.
Days get shorter and nights longer.
Faster and faster the change occurs until we reached the time of equality between light and dark. The maximum speed of change, the point of balance between day and night, is reached every year in late September. So, on the day of the equinox the Sun rises directly east, crosses our sky in the middle of its range, and sets directly west. We feel its rays for 12 hours and live without them for the other 12. At the poles of Earth the Sun moves around at the base of the horizon, the north pole feeling its last solar rays until six months from now, and the south pole rejoicing in the returning Sun to light its sky for six months to come.