The Basic Principles Of epoch sign in
Epoch versus equinoxDate-references for coordinate systemsEpochs and periods of validityChanging the common equinox and epochSpecifying an epoch or equinoxBesselian yearsJulian years and J2000Epoch in the daySee alsoReferencesNotesCitationsSourcesFurther readingExternal backlinksAstronomical quantities is often specified in any of a number of means