Why don’t you use the Jewish calendar in keeping the biblical Feasts instead of relying on the visible new moon?
The present Jewish calendar is not the same calendar the Jews used during the time of the Messiah. Up to the time of the destruction of the second Temple in Jerusalem the Sadduccees were in charge of Temple worship. The growing influence of the Pharisees culminated in their dominating Jewish worship after 70 C.E., when the Jews were driven out of Jerusalem. Modern Jewish worship is an extension of this later influence.
In Temple times visible sightings of the new moon were carried out each month in the environs of Jerusalem. Those who sighted the thin crescent were questioned by the Sanhedrin, which was charged with sanctifying the beginning of the month. When the new moon was seen and verified, a calculated calendar was obviously in use to corroborate the beginning of the 29- or 30-day month.
Certain changes and postponements are incorporated into the present Jewish calendar, established in the year 369 C.E. by Hillel II, which are nowhere found in the Bible. The Bible knows nothing of postponing a Feast day. Yet the present Jewish Calendar has four dehioth (postponements) that are here listed verbatim from The Comprehensive Hebrew Calendar by Arthur Spier:
• When the molad [conjunction] of Tishri occurs on a Sunday, Wednesday or Friday, Rosh Hahshanah is postponed to the following day.
• When the Molad Tishri occurs at noon (18h) or later, Rosh Hashanah is postponed to the next day. (Or if this day is a Sunday, Wednesday or Friday, to Monday, Thursday or Sabbath because of Dehiah a.)
• When the Molad Tishri of a common year falls on Tuesday, 204 parts after 3 a.m., i.e., 3d 9h 204 p or later, Rosh Hashanah is postponed to Wednesday, and because of Dehiah a., further postponed to Thursday.
• When, in a common year succeeding a leap year, the Molad Tishri occurs on Monday morning 589 parts after 9 a.m., 2d 15h 589 p or later, Rosh Hashanah is postponed to the next day.
There is no authorization in the Bible allowing man to transfer or delay a Feast day. Yet, one of the “religious requirements” stated is, “Yom Kippur (Tishri 10) shall not occur on the day before or after the Sabbath and Hoshana Rabba (Tishri 21) shall not occur on a Sabbath.”
Nowhere can we find that Atonement cannot occur on a Friday or Sunday. It may make sense to man’s mind that having a day between the Sabbath and the day of fasting would be desirable, but there is no biblical justification for it. Neither is there any proscription against having Hoshana Rabba occur on the Sabbath.
Interestingly, an enlightening note in The Comprehensive Hebrew Calendar states: “In more that 60 percent of all years Rosh Hashanah does not occur on the day of the Molad [conjunction] but is postponed according to one of the Dehioth. Therefore the Dehioth [postponements] are actually not the exceptions to the rule but the rule.”
In other words, man-made exceptions overrule the rules of the calendar 60 percent of the time. Therefore exceptions govern the modern Jewish calendar. We need to ask, where does the Bible teach such a thing?
Significantly, instead of beginning the annual calendar with Abib, the first biblical month of the year determined by green ears of barley (“Abib” means “green ears”), the Jewish calendar works backward from the Feast of Trumpets and Day of Atonement to set the year.
Spier’s work makes this important acknowledgment: “In the early times of our history the solution was found by the following practical procedure: The beginnings of the months were determined by direct observation of the moon…
“This method of observation and intercalation was in use throughout the period of the second temple (516 B.C.E. — 70 C.E.) and about three centuries after its destruction, as long as there was an independent Sanhedrin. In the fourth century…the patriarch Hillel II…made public the system of calendar calculation which up to then had been a closely guarded secret.”
Thus, the Jews themselves recognize that the calendar that they presently use is of more recent date and is not the calendar Yahshua followed when He walked this earth. The Israelites and Jews of old watched for the appearance of the new moon just as we do today. Observing the new moons has been the practice of Yahweh’s people down through history in obedience to Yahweh’s established heavenly calendar (Gen. 1:14; Ps. 104:19).
