Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions. It is forbidden for people to celebrate birthdays, as this is an imitation of disbelievers because Muslims didn't know this custom before. It came from the disbelievers as it is one of their customs. And, the Prophet Muhammad (Blessings and peace of Allah be upon him) ordered us to disagree with them. This is made evident from many sound Hadith. Prophet Muhammad (Blessings and peace of Allah be upon him) said also:" Whoever imitates some people, he is one of them". Narrated by Abu Dawood from Ibn Omar. And Allah knows best.