Original: 2451545.0 ) / 365.25 J2000 .0 In astronomy , an epoch is a specific moment in time for which celestial coordinates or orbital elements are specified , and from which other orbital parametrics are thereafter calculated in order to predict future position .
Simplified: In astronomy , an epoch ( or sometimes epochal moment ) is a moment in time for which the position or the orbital elements of a celestial body are specified .