Equinox are special days during the year when day and night are almost equal. There are two equinoxes, one in the spring and one in the fall. The spring, or vernal, equinox occurs around March 21 in the Northern Hemisphere and around September 21 in the Southern Hemisphere. In the Northern Hemisphere, the North Pole is tipped at its greatest angle toward the sun during the summer solstice, which occurs around June 21. In the Southern Hemisphere, around December 21, it is the South Pole's turn to be nearer. As such, in the Northern Hemisphere, astronomical spring runs from March 21 to June 21, while in the Southern Hemisphere it encompasses September 21 to December 21, thought he dates may shift slightly from year to year.