"VESTI"-Jewish Calendar. Author: Eliezer Raboukhin. "Vesti", September 14th, 2006. The article is dedicated to the explanation of distinctive aspects of the Jewish calendar. Jewish calendar is lunar-solar. It's based on lunar month and solar year. The year has 12 months: 'tishrej' (30 days), 'kheshvan' (29 or 30),' kislev' (29 or 30),' tevet' (29), 'shvat' (30), 'adar' (29),' nisan' (30), 'ijar' (29), 'sivan' (30), 'tamuz' (29), 'av' (30), 'elul' (29). In the leap year the 13th month is added and called adar aleph (30 days). It follows the month shvat. In such a case, the previous month adar remains, but it is now called not simply adar but adar bet and comes after adar aleph. The extra month adar aleph is added in order to eliminate the discrepancies between the actual length of the lunar month (29 days, 12 hours and 793 so-called khelek-parts) and that accepted in the calendar (29 or 30 days). One khelek equals approximately 3.3 seconds. Lunar year is 354 days 8 hours and 876 kheleks long. It is shorter than solar year by almost 11 days. The agreement of lunar and solar calendars is made by the fact that 19 years of solar calendar equal 235 lunar months.
To achieve the equality of both calendars in practice it is accepted that in the span of 19 years by the Jewish calendar 12 years are normal, consisiting of 12 months, and 7 years are leap years, because they have 13 months. In the 19-year cycle the third, sixth, eighth, eleventh, fourteenth, seventeenth and nineteenth years are leap years. Acording to the Jewish calendar, the beginning of a new day starts at the moment of the end of the sunset of a previous day. The count of the years starts from the beginning year of 3761 B.C. In order to translate dates from Gregorian calendar into the Jewish calendar, number 3760 is added to the number of years in Gregorian calendar (from january 1st to 29the of elul) or number 3761 (from 1st of tishrei to december 31st). In the article the author also supplies information about Jewish holidays, observances of Shabat (saturdays) and other traditions connected with the dates of Jewish calendar.