<P> On an equinox , day and night are of approximately equal duration all over the planet . They are not exactly equal , however , due to the angular size of the sun and atmospheric refraction . To avoid this ambiguity , the word equilux is sometimes ( but rarely ) used to mean a day in which the durations of light and darkness are equal . See Length of equinoctial day and night for further discussion . </P>
<P> On an equinox , day and night are of approximately equal duration all over the planet . They are not exactly equal , however , due to the angular size of the sun and atmospheric refraction . To avoid this ambiguity , the word equilux is sometimes ( but rarely ) used to mean a day in which the durations of light and darkness are equal . See Length of equinoctial day and night for further discussion . </P>
when is the day as long as the night
when is the day as long as the night
equinox
equinox