Does the above ruling and mitzva of Simcha also include the month of Nissan? Should one extend the acts of joy to consider and extend also into the month of Nissan?
A. Poskim disagree. Eishel Avrohom (Tanina 686) maintain that it only includes Adar, as the Pasuk (Esther 9: 22) mentions “The month which was turned unto them from sorrow to joy and from mourning into a good day," quoting only “the month”. However some maintain that it also includes the following month of Nissan (Eliahu Rabba (685) quoting Rashi on Taanis 29a).
Chasam Sofer (O.H. 160) adds that it is preferable to keep both months, since miracles also occurred on Nisan and thus it also creates a “Chazaka” or an established tradition that claims continuity and future joy and deliverance ,and are thus also days of Good Mazal for our nation.
Horav Shlomo Miller Slit”a maintains that the marbim besimcha ends at the end of Pesach, when the Sefira days begin.
Rabbi A. Bartfeld as revised by, Horav Shlomo Miller, Horav Dovid Pam, Horav Aharon Miller, Horav Chanoch Ehrentreu and Horav Kalman Ochs Shlit’a