In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the...

and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference...

to: Any historical era Epoch (astronomy), a moment in time used as a reference for the orbital elements of a celestial body Epoch (computing), a moment...

definition of the light-year as a unit of measurement of distance. In astronomy, an epoch specifies a precise moment in time. The positions of celestial objects...

502°/d · t where t is the time (in days) since January 1, 2000 (see Epoch (astronomy)). This shows that the smallest perigee occurs at either new moon or...

In astronomy, an equinox is either of two places on the celestial sphere at which the ecliptic intersects the celestial equator. Although there are two...

The first picosecond (10−12 seconds) of cosmic time includes the Planck epoch, during which currently established laws of physics may not have applied;...

transform Bessel window, in signal processing Besselian date, see Epoch (astronomy)#Besselian years MV Bessel, a German merchant ship in service 1928–45...

In cosmology, recombination refers to the epoch during which charged electrons and protons first became bound to form electrically neutral hydrogen atoms...

Almanac The Astronomical Almanac (new name) Ephemera Ephemeris time Epoch (astronomy) Epoch (reference date) Fundamental ephemeris January 0 or March 0 Keplerian...