The following are the general principles upon which our Calendar is
based:—
1. Twenty-nine days 12793⁄1080 hours elapse between one molad and the
next. [83]
2. An ordinary year must not have less than 353 or more than 355 days,
nor the leap-year less than 383 or more than 385 days.
3. The 1st of Tishri is fixed on the day of the molad of Tishri. There
are four exceptions (דחיות):—
a. לא אד״ו ראש. If the molad of Tishri falls on a Sunday, Wednesday,
or Friday.
b. מולד זקן. If the molad of Tishri is at noon or later.
c. If the molad of Tishri in an ordinary year is on Tuesday 3204⁄1080
A.M. or later (ג׳ ט׳ ר״ד).
d. If the molad of Tishri of a year succeeding a leap-year is on Monday
9589⁄1080 A.M. or later (ב׳ ט״ו תק״פט).
The first of these four exceptions is to prevent the Day of Atonement
from falling on Friday or Sunday, and Hoshaana-rabba from falling on
Sabbath; the third exception is to guard against having an ordinary
year of more than 355, and the last from having a leap-year of less
than 383 days.
4. The character of the year is described by three letters, the first
of which indicates the day of the week for the 1st of Tishri, the last
the day of the week for the 1st of Nisan, the middle letter, according
as it is כ, ח, or ש (=כסדר “regular;” חסרה “defective;”
שלמה “perfect”), indicates a regular year of 354 (in leap-year 384)
days, a defective year of 353 (in leap-year 383), or a perfect one of
355 (in leap-year 385) days.
The present year (September 1890 to October 1891) is, according to
Jewish tradition, [84] the year 5651 A.M. (of the Creation); its
characteristics are ב׳ ח׳ ה׳; i.e., the 1st of Tishri is on Monday;
the year is defective; and the 1st of Nisan is on Thursday. The year
is, besides, a leap-year, consisting of 13 months; it is the eighth
year of the 298th cycle (of 19 years). It is the first year of the
Septennate, or the first year after the year of release (שמטה. See
Lev. xxv.).