The school day in the UAE usually starts between 7AM and 8AM and ends between 2PM and 3PM, with a standard lunch break. The Kindergarten and primary students will have a shorter day. The extra-curricular activities run until late in the afternoon.
As for the school calendar year, it is approximately divided as given below, with slight variation from year to year and school to school.

Autumn Term – 8th September to 12th December
Spring Term – 5th January to 27th March
Summer Term – 7th April to 26th June
The school calendar will have an approximate of 172 working days for students and 185 working days for teachers. Parent-Teacher meetings are held after every term.
Although, the annual holidays are subjective to change from year to year, the general public holidays are common for all schools.