We are particularly interested in how the Hebrews originally determined the time for beginning this sacred new year and how they counted the days and the months following.
Several passages in the Bible show that the time of the months of the Hebrew year was determined by the moon. We read in Numbers 10:10: “Also in the day of your gladness, and in your solemn days, and in the beginnings of your months, ye shall blow with the trumpets over your burnt offerings, and over the sacrifices of your peace offerings; that they may be to you for a memorial before your God: I am the Lord your God.”
We also have ample evidence that the occurrence of the moon was a major factor in determining the beginnings of these months, particularly the first month of the year.
How did they know when the moon was new? Originally the Hebrews determined the time for the beginning of the new year moon of Abib by stationing observers on the hills to watch for the new moon. In the “Biblical Critical Interpretation of the Bible,” in a discussion of the history of the Jewish calendar, we find the following:
“It is certain that…the month was dated from the time when the earliest visible appearance of the new moon was announced to the Sanhedrin. That is, if this happened on the 30th day of the current month that month was considered to have ended on the preceding 29th day and was called deficient. But if no announcement was made on the 30th day, that day was reckoned to the current month which was in this case called full and the ensuing day was at once considered to be the first of the next month:”
During a large part of history—including Bible history—watchers and observers set the time. Among the Jews, the watchers would announce to the Sanhedrin, who would in turn announce the beginning of the month or the beginning of the year. In modern times this is done by calculation. Astronomers can tell within a fraction of a second when the sun crosses the line and when the moon is new.