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This page contains some in-depth information for AETD Mini-Course #55, "Time Measurement Systems".

PowerPoint Slides for AETD Mini-Course #55

Tables of Julian Days

Table of Julian Day Numbers, 1950-2100

Tables of Day of Year

Other Reference Material



  • cal.f90 - Calendar program (similar to UNIX "cal") (Fortran-90)
  • caljul.f90 - Calendar program for Julian calendar (similar to UNIX "cal") (Fortran-90)
  • greg2jd.f90 - Gregorian date to Julian day (Fortran-90)
  • jd2greg.f90 - Julian day to Gregorian date (Fortran-90)
  • doy2greg.f90 - Day of year to Gregorian date (Fortran-90)
  • greg2doy.f90 - Gregorian date to day of year (Fortran-90)
  • greg2dow.f90 - Gregorian date to day of week (Fortran-90)
  • jd2gmst.f90 - Julian day to Greenwich Mean Sidereal Time (Fortran-90)
  • leapyr.f90 - Leap year (Fortran-90)
  • easter.for - Date of Easter (Fortran-77)
  • Display the current date, time, day of year, and Julian day:
    • jd.c - C version
    • jd.f90 - Fortran-90 version



  1. Meeus, Jean. Astronomical Algorithms (2nd Ed.). Willmann-Bell, Richmond, 1998.
  2. Mueller, Ivan I. Spherical and Practical Astronomy as Applied to Geodesy. Frederick Ungar Publishing Co., New York, 1969.
  3. Seidelmann, P. Kenneth (Ed.). Explanatory Supplement to the Astronomical Almanac. University Science Books, Mill Valley, California, 1992.


  1. Reingold, Edward M. and Dershowitz, Nachum. Calendrical Calculations. (Millennium Ed.) Cambridge University Press, Cambridge, 2001.
  2. Richards, E.G. Mapping Time: The Calendar and its History. Oxford University Press, New York, 1998.
  3. Asimov, Isaac. “The Week Excuse”, in The Tragedy of the Moon. Doubleday & Co., 1973. (Includes a discussion of the World Season Calendar.)


  1. Audoin, Claude and Guinot, Bernard. The Measurement of Time: Time, Frequency and the Atomic Clock. Cambridge University Press, Cambridge, 2001.
  2. Barnett, Jo Ellen. Time's Pendulum. Plenum, New York, 1998.
  3. Gibbs, W. Wayt. "Ultimate Clocks", Scientific American, September 2002, 86-93.
  4. Guinot, B. and Seidelmann, P.K. "Time scales: their history, definition and interpretation", Astron. Astroph. (1988), 194, 304-308.
  5. Jespersen, James and Fitz-Randolph, Jane. From Sundials to Atomic Clocks: Understanding Time and Frequency. (2nd Rev. Ed.) Dover Publications, Mineola, New York, 1999.
  6. Jones, Tony. Splitting the Second: The Story of Atomic Time. Institute of Physics Publishing, Bristol, 2000.
  7. Major, F.G. The Quantum Beat: The Physical Principles of Atomic Clocks. Springer-Verlag, New York, 1998.
  8. McCarthy, Dennis D. "Precision time and the rotation of the Earth", in Transits of Venus: New Views of the Solar System and Galaxy (Proceedings IAU Colloquium No. 196 (D.W. Kurtz, Ed.), 2004.
  9. Nelson R.A., McCarthy D.D., Malys S., Levine S., Guinot B., Fliegel H.F., Beard R.L., Bartholomew T.R. "The leap second: its history and possible future". Metrologia (2001), 38, 509-529.
  10. Stephenson, F.R., and Morrison, L.V. "Long-Term Fluctuations in the Earth's Rotation: 700 BC to AD 1990", Phil. Trans. R. Soc. Lond. A (1995), 351, 165-202.


  1. Mayall, R. Newton and Mayall, Margaret W. Sundials: Their Construction and Use. Dover Publications, Mineola, New York, 2000.
  2. Rohr, René R.J. Sundials: History, Theory and Practice. Dover Publications, Mineola, New York, 1996.
  3. Stewart, Ian. "What in Heaven is a Digital Sundial?", Scientific American, August 1991, 104-106.
  4. Waugh, Albert E. Sundials: Their Theory and Construction. Dover Publications, Mineola, New York, 1973.

Daylight Saving Time

  1. Bartky, Ian R. and Harrison, Elizabeth. "Standard and Daylight-saving Time", Scientific American, May 1979, 46-53.
  2. Downing, Michael. Spring Forward: The Annual Madness of Daylight Saving Time. Shoemaker and Hoard, Washington, 2005.
  3. Prerau, David. Seize the Daylight. Thunder's Mouth Press, New York, 2005.

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Page last updated: February 13, 2013.

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