The month of Adar is the last month of the year counting from Nisan and is referred to in Tanach (abbreviation for Torah, Prophets and Writings) this way. Even in the event of a leap year, when a second Adar is added to the regular twelve months, the second Adar is also called the twelfth month. Thus, it is written in Megilat Esther: 'And in the twelfth month, which is the month of Adar;' which, according to Tradition, was the second Adar of a leap year."Rosh Chodesh" Of Adar The twelve-month sequence of months making up the Hebrew Calendar is as follows: Nisan
(Adar II - in Leap Year) Note: In an ordinary (that is, non-leap) year, there is only one Adar, namely Adar I. In a leap year, there are two Adar's: Adar I and Adar II. The schedule for leap and non-leap years won't be discussed here, because it's somewhat complicated, and not really relevant here. The months preceding and following the Adar's, namely Shevat and Nisan, as well as the Adar's, have been bolded. General Principle: Adar I (and we only refer to an Adar as Adar I when there is also an Adar II) is always "full;" that is, it contains thirty days. Also, the Adar closest to Nisan (either regular Adar in a non-leap year, or Adar II in a leap year) is always "not full;" that is, twenty nine days. Thus, the following statements are true: In a regular (non-leap) year, the following is true:
Adar is the happiest, most joyous month of the Hebrew calendar. In fact, its motto is "When Adar comes, joy is increased."
The abundance of joy in Adar is primarily due to the presence within the month of Purim. That holiday commemorates the salvation of the Jewish People from a genocidal plot by the wicked Haman, whereby he hoped to destroy the Jewish People, G-d Forbid, completely. Because of our fasting and repentance, we were able to have that heavenly decree, if not the earthly one, torn up (a decree of Achashverosh could, of course, never be rescinded).
Haman achieved the result, thank G-d, of having his plot overturned ("venahapoch hu," "it was overturned" - a theme of Purim) upon himself. Our last picture of him and his ten sons are of them dangling from the very gallows which he had prepared for Mordechai, a leader of the Jews.
Even though we are instructed in Pirkei Avot (Chapter 4, Mishnah 24) by Shmuel HaKatan, "When your enemy falls, do not be happy, and when he stumbles, let your heart not rejoice," an exception is made in the case of Haman. He represents the spirit of absolute (or nearly absolute) evil, as did his infamous ancestor, Amalek, founder of the nation which attacked the weakest of the Jews on their way out of Mitzrayim. Then the Jewish People were fresh from the Miracle of the Splitting of the sea, and their faith was still fragile, while fear of the Jews and of the awesome might of their G-d was universal among all the other nations of the world.
The Opposite of Chodesh Av
The Sages have said: 'Just as joy is reduced from the start of Av, likewise, is joy increased at the start of Adar.'
Rav Papa said: 'Therefore, a Jew engaged in litigation with a non-Jew, should avoid him during Av, which is a time of ill omen for him; and should make himself available during Adar, which is a fortunate time for him' (Ta'anit 29). For, 'Heaven revolves merit towards a day of merit,' And joy towards a day of joy. And Adar is the most joyous of all months, so much so that no evil anti-Semitic eye can affect its blessing.
When Haman wanted to discover through astrology which month would be the most 'vulnerable for Israel', he cast lots to choose the month and day. The lot fell upon the month of Adar. When Haman's plot was foiled, Adar was transformed for the Jews from a month of grief and mourning to one of rejoicing and festivity; their happiness was all the greater. And the month of Adar became the very symbol of joy to them.