The Southern Hemisphere of Earth is the half which is south of the equator. It contains all or parts of five continents (Antarctica, Australia, about 9/10 of South America, the southern third of Africa, and some southern islands in Asia), four oceans (Indian, South Atlantic, Southern, and South Pacific) and most of Oceania. Several islands off the Asian continental mainland are also in the Southern Hemisphere. Due to the tilt of Earth's rotation relative to the Sun and the ecliptic plane, summer is from December to March and winter is from June to September. September 22 or 23 is the vernal equinox and March 20 or 21 is the autumnal equinox.