The Gemara in Ta’anit 29. states:
"Just as we diminish our joy at the start of Av – when Adar begins we should heighten our joy…."
"When Adar begins – these were miraculous days for Am Yisrael: Purim and Pesach."
From Rashi we understand that the heightened joy is a result of the Purim miracle. Therefore, it makes sense that since the Purim miracle did not occur on Adar l, there is no need to rejoice in particular (unless we consider Adar l and Adar ll a kind of extended month). And so it was written in the Responsa She’ilat Yavetz (2:88). He explains: Why did Rashi write "Purim and Pesach"? Pesach has no bearing on our discussion. The Gemara says that we should read the Megilla on Adar ll in order to juxtapose one redemption (geula) to another. In other words, there is a connection between Purim and Pesach. According to this reasoning, there should be heightened joy in the Adar closest to Pesach and the redemption, but not in Adar l.
On the other hand, the Mishna states that the only differences between the two Adars is the Megilla reading and gifts for the poor. From here we can infer that regarding joy, there is no difference between them. We should heighten our joy in both months (unless we say that the Megilla reading suggests joy as well).
The Responsa Chatam Sofer (Orach Chaim 163) writes in his name, and the name of the Yerushalmi a new idea – the decree of Haman was in Adar l. Why is this so? The Megilla writes: "the 12th month, the month of Adar." Why does it add "the 12th month"? We learn from this that there were then two Adars, and this occurred in the first Adar – the 12th month. In any case, he writes that, in principle, it would be correct to mark Purim in Adar l since that was the month of the decree. However, we celebrate Purim in Adar ll in order to juxtapose one redemption to another. (We can learn from this that the idea of juxtaposing redemption to redemption indicates that that all miracles are an outgrowth of the Exodus from Egypt – see an elaboration of this concept in my Pesach Haggadah.)
If this is so, there is clearly an element of joy in Adar l, because that is when the Purim miracle occurred. The reason we celebrate in Adar ll, is the juxtaposition of redemption to redemption.
Regarding simcha, we should also learn from Halachic rulings in the matter of fast days. The Rishonim did not agree about the permissibility of fasting and eulogizing on the 14th of Adar. The Rambam ruled that it is not permissible to fast or eulogize. According to the Rosh, it is allowed. The Shulchan Aruch (697) brings this difference of opinion (at the end of Orach Chaim), and it seems he ruled that we do not say Tachanun. The Rama writes that we should even make a festive meal on the 14th.
In light of the above, should we be joyous during Adar l? If we assume that simcha depends on the Purim miracle, it seems that according to the opinions which do not permit fasting (like the Shulchan Aruch), and certainly according to opinions that it is a Mitzvah to have a festive meal (like the Rama), we should commemorate Purim on the 14th of Adar. And clearly according the opinion of the Rama, it is appropriate to heighten our joy from Adar l as well. (And certainly according to Chatam Sofer, who explained that Haman’s decree was in Adar l.)
The significance of Simcha in Adar l and Adar ll
Why do we heighten our joy in the month of Adar? As we have seen, Rashi attributes this to the miracles the Jewish people experienced during this month. It is possible that this joy is a result of those miracles. However, it is possible that joy is a preparation for celebrating the month’s miracles. One cannot simply "switch on" the joy of Purim. It needs to happen in stages. Our Sages teach us to be joyous from the start of the month, so that the joy of Purim will be more authentic, deeper and more meaningful. If this is the case, in this special year of two Adars, the preparation for Purim and Pesach is even deeper and more meaningful, and lends a deeper dimension to our joy.
While the simcha of Adar l is more limited than that of Adar ll, this year the joy of Adar ll is greater than the usual Adar. This is due to the preparatory stage of a more limited joy in Adar l. Both Purim and Pesach come after both levels of preparation and, therefore, they will have a special intensity, b’ezrat Hashem, with the powerful joy of purity and holiness, and deep gratitude to Hashem.
When one is joyful, he should remember those who struggle. Hundreds of former Gush Katif residents are still without a source of livelihood. Baruch Hashem, JobKatif has succeeded in returning 2700 Jews to the workforce, but we must continue our efforts to assist those remaining – wonderful people who were hardworking breadwinners, but who still sadly struggle in a difficult reality.
In Adar l and Adar ll may we be strengthened through joy, and, b’ezrat Hashem, we will try to strengthen others and bring them joy – and together we will attain a level of complete and true simcha.