In the northern hemisphere, the winter solstice usually falls on December 21/December 22, which is the southern hemisphere's summer solstice. At this time, the Sun appears over the Tropic of Capricorn, roughly 23.5 degrees South of the earth's equator. In the southern hemisphere, winter solstice falls on June 21/June 22, which is the northern hemisphere's summer solstice. At this time, the Sun appears over the Tropic of Cancer.
Since the winter solstice, summer solstice, vernal equinox, and autumnal equinox were probably observed for the first time by people in the northern hemisphere, these naming conventions originally corresponded to the northern hemisphere's seasons. In most reckonings, the winter solstice is midwinter.