/ Dictionary / Index J Julian Day: Meaning and Definition of Find definitions for: Jul'ian Day' Pronunciation: [key] — Astron. Astron. a serial number equal to the number of days elapsed since January 1, 4713 b.c., proposed by Joseph Scaliger in 1582 and used in astronomical calculations:J.D. January 1, 1965, at noon, Greenwich Civil Time, was Julian Day 2,438,762.0. Abbr.: Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Julian calendar Julie Related Content Daily Word Quiz: blithesome Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language