It's indeed a shame that OOXML doesn't
accommodate weekends in the Arab and Muslim Worlds.
Just a note that weekend list provided below is wrong. The weekend in
most Gulf countries is Thursday and Friday, in Jordan it's Friday and
Saturday, and in Lebanon, Tunisia, Morocco and Turkey it's Saturday
and Sunday.
While we're on the topic, anyone visiting most Arab or a Muslim
countries during Ramadan, which begins around 13th Sept. this year ,
should know that the work day and week are much shorter.