Did you know that the tilt of the Earth causes the seasons? Earth is tilted about 23.5 degrease. If it is fall above the Equator it is spring south of the Equator. It takes us 3 months to get through one full season. During the summer we have the most concentrated sunlight. The first day of winter is December 21st, Spring is March 21st, Fall is September 21st. In winter the days are have less sunlight, but in summer the days have more daylight.