Example image of eyePlorer eyePlorer map for 'Julian day': Proleptic Julian calendar Terrestrial Time Universal Time Epoch (reference date) Recorded history Week-day names Calendar Calendar date Subtraction Julian calendar Ephemeris time International Astronomical Union Sputnik 1 Year 2000 problem Dublin Republic of Ireland Gregorian calendar Aloysius Lilius American National Standards Institute COBOL Rata Die Anno Domini Common Era Proleptic Gregorian calendar Earth Heliocentric Julian Day Sun Indiction Joseph Justus Scaliger Metonic cycle Solar cycle (calendar) Julius Caesar Astronomer International Meridian Conference Prime Meridian Astronomy Edward Charles Pickering Harvard College Observatory Variable star Ptolemy Water clock Ancient Egypt Babylonia Astronomical year numbering Modular arithmetic Week Leap second List of acronyms and initialisms: G List of acronyms and initialisms: T List of acronyms and initialisms: C