Note 51 — II. OUR DUTIES. (continued 2)

The year is either an ordinary year or a leap-year, the former consisting of twelve, the latter of thirteen months. The extra month is called Adar-sheni, “the second Adar,” and is added between Adar and Nisan. It serves to adjust from time to time the lunar to the solar year;51 for there is between the lunar year—that is, the time of twelve revolutions of the moon round the earth—and the solar year, or the time of one revolution of the earth round the sun, a difference of about eleven days, the one consisting of about 354⅓, the other of about 365¼ days. In nineteen years the difference amounts to about seven months. We have therefore seven leap-years in every cycle (‏מחזור‎) of nineteen years, viz., the 3rd, 6th, 8th, 11th, 14th, 17th, and 19th.