This holiday is supposed to be four days long, and if you are fortunate enough to work for the Government it will be. But for the private sector, only two days' holiday are given. This is an ongoing cause for complaint among private sector workers in the UAE - the public sector always gets tons of holidays, and the private sector always gets less. The dates mentioned for private sector holidays are meant to be for guidance only, but no-one running a business is likely to give employees more time off than the competition, and so everyone gets the least possible.
There's also the issue of time off in lieu if the holiday coincides with the weekend. Put simply, this never happens.
The other peculiarity with these religious festivals is that the pubs close from sunset on the first day until sunset on the second. So we don't lose a whole days drinking time - just a bit of it!