Rabenu mentioned on question 5973 that it is permitted to celebrate a birthday party during the Three Weeks until Rosh Chodesh Av. Are we allowed to celebrate birthday during the Nine Days at home with only family and no music?
During the three weeks it is permitted, but during the nine days it isn't a correct thing to do, as we don't have parties during the nine days. It should be pushed off until after the nine (10) days. Kovetz Halachos ( R. S. Kaminetzsky shlit"a) Bein Hamitzarim 10-8.
Rabbi A. Bartfeld as revised by Horav Y. Hirshman, Horav Dovid Pam, Horav Aharon Miller and Horav Chanoch Ehrentreu, Horav Kalman Ochs, and Horav Dovid Bartfeld consulting in need Horav Hagaon Rav Yitzchak Berkowitz Shlit’a