Wa Rahmatullahi Wa Barakatuhu It's not my opinion. I've heard from scholars: - There is Ikhtilaf about Prophet 's birthday. There's no consensus about the date. - But Prophet 's date of passing away is obvious. - Sahabah got the greatest shock in their lives when Prophet passed away. They knew about Prophet 's date of birth very well, but they never celebrated it. - As a muslim everyone should possess the greatest affection and love for Prophet and hence how it's possible to express happiness instead of mourning? We should ponder about those points.