Private sector holiday for the Hijri New Year in UAE will be on Thursday September, 13, as per an announcement by the Ministry of Human Resources and Emiratisation. 

Also read:
Hijri New Year holiday for public sector 
Official UAE school calendar for 2018-19
UAE public holidays 2018

Work will resume on September 16 (Sunday) after the three-day-weekend. If Saturday is a working day as per your contract, then only Thursday and Friday will be off.

The Islamic New Year also known as Hijri New Year is the day that marks the beginning of a new Islamic or Hijri calendar. The first day of the year is observed on the first day of Muharram, the first month in the Islamic calendar.