Today, there is some concern regarding the current calendar that is being used by the Jews to determine the start of Feast Days.
Before the fourth century, the months in Israel were determined by observation. When the New Moon was seen to arrive, the new month began. This observational method ensured that the beginning of the Feast of Trumpets was accurate.
The Pre-Hillel II Calendar
Before the 4th century, the Jewish calendar was observational, not calculated. Each new month began with the sighting of the new moon by witnesses, confirmed by the Sanhedrin in Jerusalem (cf. Mishnah, Rosh Hashanah 1–2). Intercalation (adding a 13th month) was determined by observing the barley harvest (aviv), seasonal cycles, and equinoxes. This meant the Feasts were anchored to real-time agricultural and astronomical observations, which is likely closer to how God intended Israel to keep them (Leviticus 23:10–11; Deut. 16:1).
The Hillel II Reform (c. 358/359 AD)
Under persecution and diaspora pressure, Hillel II introduced a fixed, calculated calendar. The new system used a 19-year Metonic cycle (aligning lunar months with the solar year). Established rules of postponement (deḥiyyot) to prevent certain holy days from falling on inconvenient weekdays. This change removed dependence on reliable eyewitness testimony that and agricultural markers that resulted in accurate timekeeping for important Feast Days.
This preserved unity across Jewish communities but introduced human regulation of feast days—not direct observation.
Accuracy Concerns
The Hillel II calendar is mathematically elegant, but drifts slightly from true astronomical new moons and harvest cycles. Sometimes the Jewish calendar declares Passover (Nisan 14) a day before or after the actual astronomical new moon cycle. The fixed rules can cause Feast of Trumpets (Yom Teruah) to fall out of sync with the observable new moon. The aviv barley (which Exodus 12 and Deut. 16 link to Nisan) is no longer consulted.
Because of this, some Messianic and Karaite groups today return to observation-based calendars, aligning the Feasts more closely with biblical instructions.
Theological Implications
Since Jesus fulfilled Passover, Unleavened Bread, Firstfruits, and Pentecost on the exact days these Feast days called for, this change raises the question: Will His future fulfillment of Trumpets, Atonement, and Tabernacles be tied to the observed biblical calendar or the rabbinic Hillel calendar?
Many scholars (including my published works) suggest that God is working by His own astronomical calendar, not necessarily the rabbinic one. That means: while the Hillel II calendar is useful for Jewish tradition and unity, it may not reflect the precise timing God has in view for prophetic fulfillment.
The Primary Issues:
Trustworthiness: The Jewish calendar is reliable for Jewish liturgical life since the 4th century, but not necessarily perfectly synchronized with biblical or prophetic accuracy.
The Prophetic Application: For studying the Feasts in relation to Jesus, one should always compare the Hillel II calendar with Astronomical new moons, Seasonal barley/harvest cycles, Historical records of feast dates (Josephus, Philo).
This helps to avoid over-dependence on a man-made adjustment that may be slightly off from the true biblical markers.
The Hillel II calendar preserved Jewish unity but moved away from direct biblical observation. It is trustworthy as a cultural-religious system, but for prophetic precision (such as Jesus fulfilling the Fall Feasts), it is safer to align with God’s observable calendar—new moons, equinoxes, harvest cycles—rather than the fixed rabbinic rules.
The following is a documented side-by-side comparisson of the Hillel II (fixed rabbinic) dates for 1 Tishrei and the astronomical new-moon (conjunction), with the time offset in Jerusalem local time.
Sources and Citations
- Hillel II (rabbinic) dates for 1 Tishrei (Rosh Hashanah): Chabad & Hebcal list Sep 22 → 24, 2025 and Sep 11 → 13, 2026.
- Astronomical new-moon (conjunction): Time And Date lists Sep 21, 2025 at 19:54 UTC and widely-corroborated Sep 11, 2026 at ~03:26–03:27 UTC. (I converted to Jerusalem, UTC+3.)
- Jerusalem sunset (to mark the feast’s start): Time And Date gives the Jerusalem September 2025 table with sunset ≈ 6:35 pm on Sep 22; comparable tables put mid-September sunsets ≈ 6:47–6:50 pm in Jerusalem, consistent for 2026.
Context note (2025): That new moon coincides with a partial solar eclipse around the equinox, confirming the conjunction timing.
What this proves:
- In 2025, the rabbinic 1 Tishrei begins ~20 hours after the actual conjunction.
- In 2026, it begins ~12 hours after conjunction.
- That spread (12–20 hours here) is normal for the fixed Hillel II rules (including postponements), which are not designed to start exactly at the astronomical conjunction each year.
Categories: Robert Clifton Robinson
Robert Clifton Robinson 
This is such an important essay topic. Thank you Brother Rob for it. Jesus gave us many parables while He was here the first time. Two comes to mind:
Both of the parables indicate that those in the parable would not have fore-knowledge of the Bridegroom or Master’s arrival. The parable of Ten Virgins clearly states that the Bridegroom was delayed. The parable of The Faithful and Evil Servant also indicated that prior knowledge of the Master’s arrival was also not available. In both parables, however, there were those that were ready for the arrival, and, those that were not.
So this essay is of critical importance and the information contained within this essay should be sounded down and understood less our watch become deficient. Notice in the parable of the Ten Virgins at Matthew 25:4:
Notice there was a delay. Why is this an important piece of the parable? I ask this question because the parable does not tell us the difference between the wise and unwise group other than the amount of oil one group had over the other. This could only mean, at least to me, that the unwise group was anticipating an arrival that did not occur due to a delay, and, because it did not occur when they expected, the unwise group only had enough oil to get them to their expected arrival time. (There is more I can say about this here but it would be beyond my current point). Now given that point, I posit a comparative example below as to how I saw somethings unfold during the last Feast Of Trumpets celebration.
It was shown, rumored or stated (online) that there were people who sold everything, quit jobs, gave away assets, etc, etc, etc during the last Feast of Trumpets with the expectation that they would no longer need those assets because Christ was coming back for His church on September 23rd and they would be taken to Heaven. To me, that could be considered an act of great faith but it was clearly unwise because He did not return. And thus those people suffered a nullification or injury to their faith and reputations because the Rapture did not occur as they had expected while that expectation ignored Jesus’ warning in Matthew 25:13:
Now. I admit that I was very confident in the arrival; but, I also took to heart the warning given by both Jesus and Brother Rob to be watchful without setting a date because that date was in the purview of the Father. So, as I hoped for the arrival, I also kept my oil available and took what I felt was wise and prudent actions in my personal life to which included receiving counseling from Brother Rob either through direct communication and/or his wonderful essays. Both of which kept me grounded in scripture which allowed me to strengthened my faith when the Rapture did not occur.
Now to my second point and the beauty behind this essay. It is my belief, as it is many, that Christ will Rapture the Church during the Feasts Of Trumpets. At this time, I am completely convinced of that. Now given that statement, we can say we know every moment of that Feast. But Matthew 24:13 states:
Given that warning, two thoughts come to mind to account for the delays in the parables I used above : 1) Jesus was delaying His coming as was done in the days of Noah where the rains came seven days after Noah and his family entered the ark; and/or 2) the Jewish Rabbinic calendar is out of sync with God’s Calendar regarding the Feasts of the Lord which can cause issues in our expectations regarding them.
Given that God can foresee an end from its beginning these parables were given for our benefit in that all things are in the prerogative of the Lord . Both parables I used in this post indicate, at a minimum, three things: 1) there are two groups of people – one watching and one not,; 2) a delay in arrival; and, 3) there would be no arrival fore-knowledge.
While pointing that out, I would also like to point out something critical in the parable of the Ten Virgins. While they were slumbering and sleeping, a cry was heard.
Matthew 25:6
The parable does not say where that cry came from. It just states that it happened. I present this for that cry. Christ will be coming with the voice of archangel (!Thessalonians 4:16). The parable of the Ten Virgins shows that all heard the cry but only those that we ready were allowed into the wedding. This is what we are watching and waiting for … that cry.
Though we believe the Feast of Trumpets will be fulfilled by Christ to the letter, we should always consider that it is the Lord’s Calendar (time) that it will be fulfilled in. So given this valuable information, we should always be watching as if we believe today was that day for truly today is all we really have. Doing this will always keep us ready and ensure we have enough oil, to which, is greater point.
The Rapture of the Church is so very important because the second death will have no power over anyone taken. Now, if the Lord wishes to delay His coming to allow more to enter, then we should welcome His delay … to which … is His prerogative.
So, I want to thank you Brother Rob for this timely essay. I also want to thank you, personally, for all your wonderful counsel you gave to me and my family during the last Feast of Trumpets; and, for the days to come. I thank and praise the Holy Spirit because He led me to you.
Prayers and Blessings always.
The Beginning is Truly Near!
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