Important Dates in the Lives of Jesus and Mary 

comets. Since the ancient Chinese calendar system (a lunar calendar) is unrelated to the 

B.C.

/

A.D.

 system, this 

provides a way to independently verify the dates of sightings mentioned by the Roman historians. 

    The best modern source of information on these ancient comet sightings is undoubtedly  Cometography, A 

Catalog of Comets, Volume 1, by Gary W. Kronk. This book covers every ancient comet from 675 

B.C.

 to 

A.D.

1799, and consolidates all of the often quoted sources for ancient comet data, such as the Han shu (an ancient 

Chinese text), J. Williams, Ho Peng Yoke, A. G. Pingre, and others. Treatment is even given to mentions of 

comets found in ancient Roman texts. 

    Comets are typically visible (with the naked eye) for a period of a few days to a few weeks. They travel in an 

arc around the sun and should be visible, at some point in their path, from both Europe and China. Thus, any 

noted comet in Roman history would likely have been observed and mentioned by the ancient astronomers of 

China. It should then be possible, in a given chronology for dates in the reigns of Roman emperors, to match 

the mention of comets in Roman texts to those in Chinese texts. Comet data is examined in chapter 13 of this 

book, along with a revised chronology of the reigns of the Roman emperors, from Julius Caesar to Domitian. 

    Astronomers use a slightly modified version of the usual 

B.C.

/

A.D.

 calendar. The 

B.C.

/

A.D.

 calendar system 

does not have a year zero. For this reason, one cannot simply add or subtract to find the number of years from 

a date 

B.C.

 to a date 

A.D.

 (or vise versa). Astronomers give the year 1 

B.C.

 the number zero; 2 

B.C.

 is given the 

number negative 1; 3 

B.C.

 is negative 2, and so on. This allows one to easily calculate the number of years 

between dates by addition and subtraction. This numbering system for the years in the 

B.C.

/

A.D.

 calendar is 

called the astronomical dating system. 

Sources for Astronomy Calculations 

    This book relies on two sources for the dates and times of solar eclipses, lunar eclipses, and lunar phases. 

The first source is the astronomy software program RedShift 3, developed by Maris Multimedia, Ltd (ISBN 1 

888023 22 8).  RedShift 3 not only provides the date, time, and duration for each eclipse, but also displays a 

realistic view of the sky from any point on earth, at any point in time stretching back for thousands of years. 

One can use this software to watch an eclipse much as it might have been seen from Jerusalem, or Rome, or 

some other location. This software provides dates, times, and other information for eclipses, lunar phases, and 

the Spring Equinox. 

    The second source for data on solar and lunar eclipses and lunar phases is Fred Espenak's Eclipse Home 

Page at the NASA/GSFC Sun Earth Connection Education Forum: 

NASA/GSFC Sun Earth Connection Education Forum 

http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html 

Five Millennium Catalog of Solar Eclipses 

http://sunearth.gsfc.nasa.gov/eclipse/SEcat/SEcatalog.html 

Five Millennium Catalog of Lunar Eclipses 

http://sunearth.gsfc.nasa.gov/eclipse/LEcat/LEcatalog.html 

Five Millennia Catalog of Phases of the Moon 

http://sunearth.gsfc.nasa.gov/eclipse/phase/phasecat.html 

    Eclipse predictions are provided courtesy of Fred Espenak, NASA/Goddard Space Flight Center.  All 

eclipse calculations are by Fred Espenak, and he assumes full responsibility for their accuracy. 

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    The Five Millennia Catalog of Phases of the Moon provides:   the date and time (Greenwich Mean Time) of all 

phases of the Moon for a period covering five millennia. This data is provided primarily to assist in historical 

research projects. 

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