kal´en-dar (Latin calendarium, “an account book,†from calendae, “day on which accounts were dueâ€): The Hebrew or Jewish calendar had three stages of development: the preëxilic, or Biblical; the postexilic, or Talmudic; and the post-Talmudic. The first rested on observation merely, the second on observation coupled with calculation, and the third on calculation only. In the first period the priests determined the beginning of each month by the appearance of the new moon and the recurrence of the prescribed feasts from the vernal and autumnal equinoxes. Thus, the month Abı̄b ('aÌ„bhı̄bh), the first month of the year according to the Levitical law, in which the Passover was to be celebrated, was determined by observation (; Dt 16). After the exile more accurate methods of determining the months and seasons came into vogue, and calculation was employed to supplement and correct observations and the calendar was regulated according to the Babylonian system, as is evidenced by the names of the months which are derived from it. In later times the calendar was fixed by mathematical methods (see the article “Calendar†in the Jewish Encyclopedia). The difficulty of ascertaining the first day of the new moon by observation, in the early period, led to the celebration of two days, as seems to be indicated in . We have only four names of months belonging to the preëxilic period, and they are Phoenician. Of these 'Abı̄b ('aÌ„bhı̄bh) was the first month, as already indicated, and it corresponded to Nisan (nı̄sÌ£aÌ„n) in the later calendar. It was the month in which the Exodus occurred and the month of the Passover (; ; ; ).
The 2nd month of this calendar was Ziv (zı̄w) (, ); Ethanim ('eÌ„thaÌ„nı̄m) was the 7th (), corresponding to Tishrı̄ of the later calendar, and BuÌ„l ‛buÌ„l' the 8th, corresponded to MarhÌ£esvan ‛marhÌ£eshwaÌ„n' (). There were course other month names in this old calendar, but they have not come down to us. These names refer to the aspects of the seasons: Thus Abı̄b ‛'aÌ„bhı̄bh' means grain in the ear, just ripening (; ); Ziv ‛zı̄w' refers to the beauty and splendor of the flowers in the spring; Ethanim ‛'eÌ„thaÌ„nı̄m' means perennial, probably referring to living fountains; and BuÌ„l ‛buÌ„l' means rain or showers, being the month when the rainy season commenced. The full calendar of months used in the postexilic period is given in a table accompanying this article. The names given in the table are not all found in the Bible, as the months are usually referred to by number, but we find Nı̄sÌ£aÌ„n in and ; Ṣı̄waÌ„n in ; TammuÌ„z in , although the term as here used refers to a Phoenician god after whom the month was named; 'ĔluÌ„l occurs in ; Kı̄sÌ£leÌ„w (the American Standard Revised Version “chislevâ€) in and ; TeÌ„bheÌ„th in ; ShebhaÌ„tÌ£ in and 'AÌŒdhaÌ„r in and several times in Est. These months were lunar and began with the new moon, but their position in regard to the seasons varied somewhat because of the intercalary month about every three years.