The Julian Day Calendar
This calendar is extensively used in astronomy, oceanography, and other sciences. It must not be confused with the Julian civil calendar.
This calendar was devised in 1582 by Josephus Justus Scaliger; the Julian date for a given calendar date is the number of days that have elapsed for that date since noon (by Universal Time [U.T.]) on January 1, 4713 B.C. It is based on a time interval 7,980 years long, which Scaliger called the Julian period. For example, noon (12:00 U.T.) on January 1, 1996 is Julian Day J.D. 2,450,084.0 = 1.5 January 1996 U.T.
Branley, Franklyn M., Mark R. Chartrand III, and Helmut K. Wimmer. Astronomy. New York, Thomas Y. Crowell Co., 1975, pp. 407–415.
Oriti, Ronald A., and William B., Starbird. Introduction to Astronomy. Encino, CA: Glencoe Press, 1977, pp. 45-51.
Frederick R. West
Science EncyclopediaScience & Philosophy: Calcium Sulfate to Categorical imperativeCalendars - Types Of Calendars, The Development Of Our Present (gregorian) Calendar, Possible Future Calendar Reform And Additions