during which two months (equinoxes) do all locations on earth experience 12 hours of daylight
Equinox An equinox is commonly regarded as the moment the plane of Earth's equator passes through the center of the Sun's disk,[2] which occurs twice each year, around 20 March and 22-23 September. In other words, it is the point in which the center of the visible sun is directly over the equator. This simplified, but incorrect, understanding of Earth's orbital motion can lead to errors of up to 69 seconds from the actual time of equinox.
Midnight sun Around the summer solstice (approximately 21 June in the Northern Hemisphere and 22 December in the Southern Hemisphere), the sun is visible for the full 24 hours, given fair weather. The number of days per year with potential midnight sun increases the closer towards either pole one goes. Although approximately defined by the polar circles, in practice the midnight sun can be seen as much as 55 miles (90Â km) outside the polar circle, as described below, and the exact latitudes of the farthest reaches of midnight sun depend on topography and vary slightly year-to-year.