Kedushah vs. Simḥah

Question

As pointed out here, and noted in the comments, there is no Taḥanun recited the entire month of Nisan. According to MB 429:2(7) it's because of Kedushah.

I was wondering if someone can weigh in on the question I asked in my comment on this answer.

"What is the defining difference between Kedushah and Simchah in terms of saying Tachanun? We certainly recite it in Eretz Yisrael and in Yerushalayim, where there is a higher level of Kedushah, and we do not recite it when there is a groom present, so is there something about a day - or month - of Kedushah that gives it some level of Simchah that eliminates the need for reciting Tachanun, or does a certain level of Simchah create an atmosphere of Kedushah (or vice versa)? Or does there need to be some level of Kedushah in a Simchah-dik atmosphere together?"

Any thoughts?

Answer 1

R' Shneur Zalman of Liadi, when discussing this minhag (and citing earlier sources about it), adds that we consider these days כעין יום טוב - "akin to a Yom Tov" (Orach Chaim 429:9).

In Hilchos Nefillas Apayim (131:5), he writes that tachanun is omitted when a groom is present, מפני שיום טוב שלו הוא - "because it is his Yom Tov"; on the day of a circumcision, מפני שמצות מילה בשמחה קבלו עליהם - "because the Jewish People accepted the mitzvah of circumcision joyfully"; and in the house of a mourner (G-d forbid), מפני שז' ימי אבילות הוקשו לז' ימי החג לענין איסור עשיית מלאכה - "because the seven days of mourning are compared to the seven days of Yom Tov insofar as the prohibition against work."

So it would seem that according to his view, at least, tachanun is omitted on days that are similar to Yom Tov in having greater simchah, not necessarily kedushah.