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abstraction > mathematical concept > unit > non SI unit > day

day (d)
subject			fact

day	has symbol d
	has value 86400.51 seconds
	has value in SI unit 24 h = 86400 s
	has definition An interval of 86400.51 seconds, unless otherwise indicated.
	is a kind of time unit
	is a kind of non SI unit
time unit	is a unit of time
unit	has historical origin
	represents

Kinds of day :

• mean solar day (3 facts) - The mean length of time between two successive culminations of the Sun (i.e., the mean period from apparent noon to apparent noon).
• sidereal day (3 facts) - The length of time between two successive meridian transits of the vernal equinox (cf. mean solar day). Because of precession the sidereal day is about 0.0084 second shorter than the period of rotation of Earth relative to a fixed direction (23^h56^m4^s.099).