The Biblical Solar Calendar (Zadokite or Qumran, Dead Sea Scrolls solar calendar) is structured in a highly organized way. The calendar is exactly 364 days. Since the actual solar year is 365.2422 days, this calendar would gradually fall out of sync with the equinoxes and seasons unless some form of intercalation (adding additional calendar time) was applied.
However, the exact method remains speculative, as the Dead Sea Scrolls do not explicitly describe a formalized intercalation rule. Since no intercalation method can be firmly established by a direct description, we must use deductive reasoning to determine what to do.
Here are the facts we do know:
- The Biblical Solar Year is 52 weeks exactly (364 ÷ 7 = 52)
- The Biblical Solar Year consists of 12 months (each with a fixed 30 days, plus for four intercalary days marking the transitions between the seasons)
- Every year begins on the Fourth day of the week (Wednesday), the day of creation for the heavenly lights (Genesis 1:14-19)
Signs in the Heavens
Let’s begin the process of this deductive reasoning for the things not specifically stated.
Then God said, “Let there be lights in the expanse of the heavens to separate the day from the night, and let them be for signs and for seasons and for days and years;
(Genesis 1:14)
Clearly the indicators for the beginning of the year are celestial. There is no hint at all in any of the Scriptures that the beginning of the year is dependent on an agricultural event. Those who use such signs as the condition of barley are simply following Jewish traditions that violate the Scriptures.
We do know the beginning of the year is in the Spring (Exodus 12:2). The most obvious celestial sign in the Spring is the equinox (more specifically, the equilux when periods of light and darkness are equal). Therefore, the beginning of the year cannot occur until the Spring equinox has occurred. And, as stated above, the year always begins on the fourth day of the week, the day the heavenly lights (sun, moon, and stars) were created.
That makes it pretty easy to determine that the beginning of the year is on the fourth day of the week (Wednesday) that immediately follows the Spring equinox.
The Need for Intercalation
The upcoming year, beginning in the Spring of the Gregorian year 2025, provides a perfect example of when and why intercalation is needed. The current year (as I write this in the Winter of 2025) will end – Day 31 of the 12th month, falling on the third day of the week – before the Spring equinox has occurred. Therefore, it is necessary to add an additional week to the end of the 364-day calendar. The new year will begin on the fourth day of the next week.
Specifically referencing the Gregorian calendar dates, the Biblical Solar Year ends on Day 364, or March 18, 2025. However, the new Biblical Solar Year cannot begin the following day, on March 19, because the Spring Equinox has not yet occurred. The Spring Equinox is at 09:02 UTC on March 20, 2025. To accommodate, it is necessary to add an intercalation week from March 19 to March 25. The new Biblical Solar Year then begins on Wednesday, March 26, 2025.
Because the Biblical Solar Year is 364 days and the astronomical solar year is 365.25 days, this additional intercalation week will be needed every 5 or 6 years. Though it is added to the end of the previous year, it technically is not a part of the 364 day year. However, it should be noted that adding this needed intercalation week does not affect Yah’s calendar. There are no commanded Feasts or other observances during the winter season.
Conclusion
Adding an intercalation week is necessary every 5 or 6 years in order to keep the seasons aligned with the astronomical solar cycle. It assures the associated Biblical Feasts occur at the right time. The important standard is that the new Biblical Solar Year always begins on the fourth day of the week immediately following the Spring equinox.
For a very detailed explanation of the Biblical Solar Calendar, check out The Scriptural Calendar – Reconstructing the 364-Day Calendar and the Intercalation Method by Christopher Collins.