More evident from high latitudes, a hemisphere's winter solstice occurs on the day with the shortest period of daylight and longest night of the year, when the sun's daily maximum elevation in the sky is at its lowest. Although the winter solstice itself lasts only a moment in time, the term sometimes refers to the day on which it occurs. Other names are "midwinter", the "extreme of winter" (Dongzhi), or the "shortest day". In some cultures it is seen as the middle of winter, while in others it is seen as the beginning of winter. In meteorology, winter in the Northern Hemisphere spans the entire period of December through February. The seasonal significance of the winter solstice is in the reversal of the gradual lengthening of nights and shortening hours of daylight during the day. The earliest sunset and latest sunrise dates differ from winter solstice, however, and these depend on latitude, due to the variation in the solar day throughout the year caused by the Earth's elliptical orbit (see earliest and latest sunrise and sunset).