date of reference

Thesaurus

Noun

1.

date of reference - (astronomy) an arbitrarily fixed date that is the point in time relative to which information (as coordinates of a celestial body) is recorded epoch astronomy, uranology - the branch of physics that studies celestial bodies and the universe as a whole date - the particular day, month, or year (usually according to the Gregorian calendar) that an event occurred; "he tried to memorizes all the dates for his history class"