Two families in the same town, both keeping the feasts faithfully, can arrive at Yom Teruah two days apart. Here is why — without anyone being wrong.
If you are new to this, the disagreement can be alarming. It shouldn't be. Every position below is held by people who take the text seriously, and the differences come from questions Scripture does not settle explicitly.
The two questions everything turns on
1. When does a month begin? Scripture ties the months to the moon but never says how the new moon is determined. Do you wait until a human being in the land actually sees the first crescent, or do you calculate the conjunction in advance?
2. When does the year begin? Exodus 12:2 makes the month of the aviv the first month. Aviv describes barley at a particular stage of ripening. So does the year begin when the barley in Israel is found to be aviv, or by a fixed calculation that keeps the calendar aligned with the seasons?
Answer those two differently and you get different dates. That is the whole of it.
The main reckonings
| Reckoning | New month | New year | Who keeps it |
|---|---|---|---|
|
Rabbinic / calculated (Hillel II) |
Calculated conjunction, fixed in advance | Fixed 19-year cycle with leap months | Most Jewish communities worldwide; most Messianic Jewish congregations |
| Sighted moon | First visible crescent, observed from Israel | Usually paired with aviv barley | Karaite Jews; many Hebrew Roots fellowships |
| Aviv barley | Usually sighted crescent | Barley in Israel found at the aviv stage | Hebrew Roots households, often alongside sighted moon |
|
Solar / Zadokite (Enoch, Jubilees) |
364-day solar year, no lunar months | Fixed solar | A small minority; produces dates unlike any of the above |
The practical result: rabbinic and sighted-moon dates usually land within a day or two of each other, occasionally further. Solar reckonings can diverge by weeks.
What aviv barley actually looks like
This is the part most people have never seen. Aviv is not "ripe" — it is a specific developmental stage where the grain has filled enough to be parched by fire but is not yet hard. Determining it means walking fields in Israel and examining heads of barley by hand.
Aviv barley field footage · Nehemia Gordon — Karaite Jewish scholar who does not profess Yeshua as Messiah. We include his work because it is the most careful documentation of barley inspection available anywhere and is relied on across the Hebrew Roots world. Weigh it as Jewish scholarship, not Messianic teaching.
“Reaping the Benefits of the Medieval Aviv Calendar” · Nehemia Gordon — Karaite Jewish. The historical background to how the calendar came to be calculated rather than observed.
“Time: Our Creator's Calendar” · 119 Ministries — Hebrew Roots. The case for observational reckoning, from a Torah-observant believing perspective.
Calendar resources
- Hebcal — the standard calculated calendar. Date conversion, candle-lighting times, Torah readings. Mainstream Jewish.
- Chabad holiday calendar — calculated dates with observance guides. Mainstream Jewish, Chabad-Lubavitch.
- Karaite Korner: the New Moon — the case for the visible crescent rather than the conjunction. Karaite Jewish.
- Devorah's Date Tree — new moon sighting reports and barley inspections from Israel. Widely used by sighted-moon households. Published via Patreon and social channels.
We list these so you can find the one your household keeps. Listing is not endorsement of any reckoning over another.
Free printable calendar — all of 5787's appointed times on one page, rabbinic dates with the sighted-moon caveat printed right on it, and this page's two questions summarised on the back.
Common questions
Which calendar does this shop use?
We publish rabbinic dates because they are the most widely used and the most predictable, and we say so every time we print one. Where a product is tied to a particular reckoning, we label which. We are a bookshop, not a beit din.
Does it matter if I get the day wrong?
Every position here is held by people trying to obey. If you keep the day your congregation keeps, in good conscience, you are not doing something reckless. The households that get into trouble are usually the ones who decide the question makes everyone else unfaithful.
Why does a day start at sunset?
Because Genesis counts it that way — there was evening and there was morning. This trips up more new households than anything else, usually as a meal eaten twenty-four hours late.
What is a leap month?
Twelve lunar months run about eleven days short of a solar year, so without correction the spring feasts would drift into winter. A thirteenth month, Adar II, is added periodically — by fixed cycle in the rabbinic calendar, by barley observation in aviv-based reckonings.