A Julian date or day number is the number of elapsed days since the beginning of a cycle of 7,980 years invented by Joseph Scaliger in 1583. The purpose of the system is to make it easy to compute an integer (whole number) difference between one calendar date and another calendar date. The 7,980 year cycle was derived by combining several traditional time cycles (solar, lunar, and a particular Roman tax cycle) for which 7,980 was a common multiple. The starting point for the first Julian cycle began on January 1, 4713 B.C. (Gregorian calendar - expressed in the ISO date format as "-4713-01-01 G") and will end on January 22, 3268 (3268-01-22 G). The following day will begin the first day of the second Julian date period (or 7,980 year cycle). i hope that this will help's you i just search it. cowboy...

Julian date (JD) is a system of time measurement for scientific use by the astronomy community. Julian date is recommended for astronomical use by the International Astronomical Union. http://en.wikipedia.org/wiki/Julian_day