The 91st Day sun calendar is based on the doctrine that the year's seasons are divided into four equal parts of 91 days each.  Thus, it finds 364 days to a calendar year, with the master sign day being the day of the Vernal Equinox Day.  The greatest weight of evidence its believers use to substantiate this is are the two extrabiblical books of Jubilees and Enoch.  In fact they attribute the majority of their doctrine to "revelations" about yearly divisions as found in these books, and comparatively very little of their "final arguments" are based on the Bible.  Before exposing these books as being of historical interest at best and not divinely inspired Scripture, let's digress for a moment to discuss the  "lost books of the Bible" in general.

   Are there "lost books of the Bible"?, and are they of divine inspiration of the Holy Spirit?  To answer the first question --- yes there are some books apparently missing from our standard Bible texts.  These include "The Book of the Law of God" (Josh.24:26); "The Books of the Wars of Yahweh" (Num.21:26); "The Books of Nathan the Prophet and Gad the Seer" (I. Chron.29:29); "The Prophecy of Ahijah, The Visions of Iddo" (II Chron.9:29); "The Book of Jehu" (II Chron. 20:34).  The point is, that these books are mentioned in our other divinely inspired books (that bear witness between themselves), and we know the true lost books would be of value if found and validated as authentic.  However, if we actually have a book (such as Jubilees and Enoch) then they can't be "lost" in the first place.  The Bible student readily knows that there are plenty of so called "lost books of the Bible" that all share the distinction of being so wild in their spiritual fantasies, chronological errors, language text blunders, or lack of credibility of its authors, that no qualified researcher of ancient Bible texts dare include them as being divinely inspired.  (answering the second question above)

   What has unfortunately developed with the many so called lost books of the Bible is that they have become convenient tools which those spouting unbiblical mystical doctrines use to supposedly "prove their theological points". A common thread of the "lost books" we see available from mail order companies is that they are usually so vague in their content that they read like an Edgar Cayce novel or New Age literature, from which anybody can cite some generic point within them, slap on their own personal interpretation, and invent a "long lost but now discovered doctrine". Some of these books may be of linguistic worth in studying an ancient language of a geographic area, or for an aid in archaeology in deciphering clay pots and bowls, but they fail miserably in standing the test of being divinely inspired writings. 

    The books of Jubilees and Enoch are among those that fail the test as well, even though for some strange reason these two books have made a popular comeback within several Saxon Israel Kingdom circles presently.  It should further be pointed out that neither the Book of Jubilees nor the Book of Enoch are part of the Apocryphal Books of the original 1611 King James Version Bible, the Septuagint, or the Latin Vulgate ---- and for good reason too!   No Western Saxon Bible translator down through the many centuries would dare include them in their church Bibles for fear of losing credibility and the deserved scholarly criticism that might follow.  We'll examine each of these two books separately in the next two sections as to their spiritual validity, and see how they compare to Yahweh's calendar of Sabbath and Feast Day events clearly given  in our Christian Scriptures.