Today marks Mawlid an-Nabi, or festival of the birth of the Prophet Muhammad (PBUH). However its unclear where the tradition of this celebration originated. Neither the Prophet nor his close companions or people who followed him marked or commemorated his birthday as a special day.

From what I have read the Mawlid celebration is not considered part of the Islamic religion. It is rather part of a cultural side of Muslim life, and also not celebrated by all parties. Observing the day is considered by Sunni and Shia Scholars to be necessary and permissible in Islam.They see it as a praiseworthy event and positive development. However the day is not a holiday in Saudi, nor is it celebrated by Wahabi or Deobandi Scholars.
More details thanks to Wikipedia are here if you fancy.
Enjoy the day off in the UAE.