Q. Can one make a seudas hodaah for a medical miracle that occurred recently during the month of Av, or should one better wait until next month?
A. From the following questions it would appear that you may do the seuda already after Tisha Beav.
On question 1801 we were asked the following: The Mishna Berura (551,1), says that “Mishenichnas Av Memaatin Besimcha” (When the month of Av begins we should reduce joy), applies until Rosh Chodesh Elul. Does that mean that one should continue with feelings of sadness and sorrow for the churban during the whole month of Av?
To what we answered: Actually, the Mishna Berura (ibid.) mentions the whole month of Av in regards to avoiding a court case with a Gentile during the month of Av, because the month is not of good mazal. Even on that he quotes the Korban Nessanel, that one should abstain only at least after Tisha Beav.
Kaf Hachaim (ibid. 1), Aruch Hashulchan (ibid. 11) and others maintain that the tenth of Av is also included.
However, other Poskim are of the opinion that one should abstain until after Shabbos Nachamu, and from then one may attend weddings (Mincha Elozor 3: 66) or until after Tu Beav, whichever is first (Hisorerus Hateshuva 2: 171).
Others mention only Tu Beav as the limit of restrictive joy. (Hagoos Chasam Sofer, gilyon O.H. ibid., Yafe Lalev quoted by Kaf Hachaim ibid.).
On question 1406 in regards to postponing a necessary medical surgery on the third week of the month, we wrote “Shulchan Aruch (O.H. 551: 1) rules that from the beginning of the month of Av one should minimize joy. He adds that it is a month when the mazal is inferior and unfortunate (reiya mazleh), and one should avoid going to trial on this month. Beir Heitev (ibid 2) explains that from the Talmud (Taanis 29a) it would seem that it applies to the complete month. Mishna Berura (ibid. 2) quotes from the Zohar that at least one should abstain until after Tisha Beav.
Kedushas Levi mentions that the month Av is divided into two distinct sections. Part one belongs to Arur (accursed, implied by the alef of Av) and part B stands for baruch (blessed, inferred on the beis of Av), and this lat one contains good mazal.
Chasam Sofer (Droshos 2: p. 331) maintains that a new month begins with Tisha Beav and is named Menachem. Tisha Beav is day one of that new month (See Yerushalmi Taanis 4: 5, and Yechezkel 26: 1; It came to pass in the eleventh year on the first of the month, that the word of Hashem came to me).
However, Machazik Brocho (Chida 551) and other follow the Beir Heitev’s opinion that the “reiya mazleh” extends for the complete month.
Horav Shlomo Miller’s Shlit’a opinion is that in need a person can be lenient after Assara Beav. (Tenth of Av).”
In regards to to your question, Horav Shlomo Miller’s Shlit’a opinion is that it suffices until after Tisha Beav.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit’a