Question

Is the Jubilee year (50th) is counted as the 1st year of the new Jubilee Duration OR does the new Jubilee duration begin in the "51st year".

Answer

That very point is disputed by the great Talmudic commentators. So I can't give a definite answer on that one.

Question

Do Hebrew years, work out to be the same duration as Christian years. Does a 1000 Hebrew years account for the same period of time as 1000 Christian years?

Answer

Not exactly. The Jewish calendar is based on both the solar and lunar cycles. Every Jewish month begins with the New Moon. To ensure that the holidays occur in their proper seasons (e.g. Passover in the springtime, and Sukkot in the fall), a "leap month," or extra month, is added 7 times every 19 years. For 3,300 years, the Jews have successfully synchronized the lunar calendar with the solar cycle.

Thus, the Jewish calendar is "Luni-Solar." It is in contrast to our civil calendar, the Gregorian, which is purely solar, and in which the months have completely lost their relation to the moon. But it is also quite different from the Mohammedan calendar, an absolutely lunar system, in which every month follows the moon closely but wanders through all four seasons during the period of 33 years.

Based on the Talmud (Rosh Hashana 25a), the Jewish months are calculated at 29.53059 days.

It took the modern world many centuries to arrive at a figure this accurate of the length of the lunar month. After years of research based on calculations using satellites, hairline telescopes, laser beams and super- computers, scientists at NASA determined that the length of the "synodic month," i.e. the time between one new moon and the next is: 29.530588 days. Quite remarkable what the Talmudic sages knew from the tradition given by God to Moses at Mount Sinai!

By contrast, the Gregorian calendar has experienced many difficulties in trying to properly "align itself with the stars." The following is from The New Encyclopedia Britannica (1990 Micropeadia, Volume 2, p. 740):

The origin of the calendric system in general use today - the Gregorian calendar - can be traced back to the Roman republican calendar, which is thought to have been introduced by the fifth king of Rome, Tarquinius Priscus (616-579 BCE)...

By 46 BCE the calendar had become so hopelessly confused that Julius Caesar was forced to initiate a reform of the entire system. Caesar invited the Alexandrian astronomer Sosigenes to undertake this task. Sosigenes suggested abandoning the lunar system altogether and replacing it with a tropical year of 365.25 days. Further, to correct the accumulation of previous errors, a total of 90 intercalary days had to be added to 46 BCE, meaning that January 1, 45 BCE, occurred in what would have been the middle of March. To prevent the problem from recurring, Sosigenes suggested that an extra day be added to every fourth February. The adoption of such reformatory measures resulted in the establishment of the Julian calendar, which was used for roughly the next 1,600 years.

During that time, however, the disagreement between the Julian year of 365.25 days and the tropical year of 365.242199 gradually produced significant errors. The discrepancy mounted at a rate of 11 minutes 14 seconds per year until it was a full 10 days in 1545, when the Council of Trent authorized Pope Paul III to take corrective action. No solution was found for many years. In 1572 Pope Gregory III agreed to issue a papal bull drawn up by the Jesuit astronomer Christopher Clavius. Ten years later, when the edict was finally proclaimed, 10 days in October were skipped to bring the calendar back in line.

* * *

The following is from "Blessing of the Sun" by Rabbi J. David Bleich (ArtScroll-Mesorah Pub., pp. 47-48)

The Julian calendar was adopted in Rome in the year 46 BCE. When the Julian calendar was first introduced the vernal equinox fell on the 25th day of March. By the year 1582 the equinox had retrograded to March 11th. In 1582 Pope Gregory XIII directed that 10 days be suppressed or dropped from the calendar. This was accomplished by designating that October 5, 1582, become October 15th.

The dates October 5 through October 14 were simply eliminated from the calendar for the year 1582. In this way the vernal equinox which then would have occurred on March 11th was shifted forward to March 21st. March 21st was selected by Gregory XIII as the date of the vernal equinox and the beginning of spring because the equinox fell on March 21st in the Julian calendar in the year 325, the year in which the Council of Nicaea was held. It was the Council of Nicaea which promulgated rules for setting the date of Easter so that it would occur after the equinox but would not coincide with the Jewish Pesach. It was disdain for Jews and Judaism that prompted purposive error and suppression of historical reality in establishing the ecclesiastical calendar. At the time of Gregory XIII this policy was aptly portrayed in a popular epigram describing the promulgators of the church calendar as individuals who chose to be "wrong with the moon rather than right with the Jews."

Question

I am trying to work out when genuine Jubilee years have occured and work my
way back to the very first one.

Answer

The first one was 50 years after the Jewish people entered the Land of Israel, which was in the Jewish year 2448, corresponding to 1272 BCE. Hence the first Jubilee was in the year 1222 BCE.