Adar (Hebrew: Adar; from Akkadianadaru) is the sixth month of the civil year and the twelfth month of the ecclesiastical year on the Hebrew calendar, roughly corresponding to the month of March in the Gregorian calendar. It is a winter month of 29 days. The key Purim-related liberating wartime events and main mention of the month appear in the holy scripture of Esther 9, its last book.
In leap years, it is preceded by a 30-day intercalary month named Adar Aleph (Hebrew: ?', Aleph being the first letter of the Hebrew alphabet, also known as "Adar Rishon" (First Adar) or "Adar I") and it is then itself called Adar Bet (Hebrew: ?', Bet being the second letter of the Hebrew Alphabet, also known as "Adar Sheni" (Second Adar) or "Adar II"). Occasionally instead of Adar I and Adar II, "Adar" and "Ve'Adar" are used (Ve means 'and' thus: And Adar). Adar I and II occur during February-March on the Gregorian calendar.
Based on a line in the Mishnah declaring that Purim must be celebrated in Adar II in a leap year (Megillah 1:4), Adar I is considered the "extra" month. As a result, someone born in Adar during a non leap year would celebrate their birthday in Adar II during a leap year. However, someone born during either Adar in a leap year will celebrate their birthday during Adar in a non-leap year, except that someone born on 30 Adar I will celebrate their birthday on 1 Nisan in a non-leap year because Adar in a non-leap year has only 29 days.
During the Second Temple period, there was a Jewish custom to make a public proclamation on the first day of the lunar month Adar, reminding the people that they are to prepare their annual monetary offering to the Temple treasury, known as the half-Shekel.
13 Adar (II in leap years) - Fast of Esther - on 11 Adar when the 13th falls on Shabbat - (Fast Day) 14 Adar (II in leap years) - Purim 14 Adar I (does not exist in non-leap years; Karaites celebrate in Adar II) - Purim Katan 15 Adar (II in leap years) - Shushan Purim - celebration of Purim in walled cities existing during the time of Joshua
17 Adar (II in leap years) - Yom Adar celebration feast
7 Adar (1828) - Death of Rebbe Isaac Taub of Kalov, founder of the Kalover Hasidic dynasty, and a student of Rabbi Leib Sarah's.
9 Adar (1st century BCE) - Academic dissension between Beit Hillel and Beit Shammai, erupted into a violent and destructive conflict over a vote on 18 legal matters leading to the death of 3,000 students. The day was later declared a fast day by the Shulchan Aruch, however, it was never observed as such.
20 Adar (1616 CE) - 'Purim Vinz': downfall of Vinzenz Fettmilch and triumphant return of the Jews of Frankfurt under Imperial protection. The day was established as a community Purim for generations and to this day the Washington Heights community does not recite Tachanun on this day.
24 Adar (1817) - The Blood Libel, the accusation that Jews murdered Christian children for their blood, declared false by Czar Alexander I. Nevertheless, nearly a hundred years later the accusation was officially leveled against Mendel Beilis in Kiev.
28 Adar (1524) - the Jews of Cairo were saved from the plot of Ahmad Pasha, who sought revenge against the Jewish minister Abraham de Castro who had informed Selim II of Ahmad's plan to cede from the Ottoman Empire. To this day, Adar 28th is considered the Purim of Cairo, with festivities including a special Megilah reading.
Azar or Adhar (Arabic: ?) is the name for the month of March in the Levant.
^No 24 WA21946, The Babylonian Chronicles, The British Museum
^Mordechai Margoliouth (ed.), Halakhot Eretz Yisrael min ha-Genizah, Mossad Harav Kook: Jerusalem 1973, p. 142 (Hebrew). The Scroll of Fasting places this event on the 12th day of the lunar month Adar.