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time unit comparison table

Subject	has definition	has value	has symbol	has value in SI unit	has synonym	is a kind of	is an instance of
aeon	In astronomical terms, 1000 million years.				eon		time unit
cosmic year	Time the Sun takes to "orbit" in galactic rotation: about 225 million years.	225 million years					time unit
day	An interval of 86400.51 seconds, unless otherwise indicated.	86400.51 seconds	d	24 h = 86400 s		non SI unit
month	The period of one complete synodic or sidereal revolution of the Moon around the Earth; also a calendrical unit that approximates the period of revolution.					time unit
second unit						time unit
week	An arbitrary period of days, usually seven days; approximately equal to the number of days counted between the four phases of the Moon. (See lunar phases.)	7 days				time unit
year	A period of time based on the revolution of the Earth around the Sun.					time unit

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