text: That period is called the "polar night", nothing more fancy than that.\n\n\n\nThe winter solstice is the day, all over the world, that the days are the shortest.  In the northern hemisphere this is on 21 or 22 December, in the southern hemisphere it's on 21 or 22 June.\n\nThe summer solstice is the day when the days are the longest (on 21 or 22 June in the northern hemisphere and 21 or 22 December in the southern).\n\nSo, on the solstices the length of the day and the altitude of the sun (at noon) are the maximum or the minimum compared to all the other days of the year.\n\nAn equinox is when the sun passes over the equator, which happens twice every year, around March 21 and September 23.  On those two days the night and the day have equal length on every location in the world.