"I think the reason is simply political. Hamas considers the Fayyad government as illegal and does not want to recognize their decree. Once a unity government is establishes, one could expect Hamas to switch the weekend in the same way." - Tosefta Agreed. The fact that both sides took action shows that it is a political issue. It is also after the US decree in Iraq, a political statement. Abbas has acted in a fashion that makes him look like a lackey. I doubt if he would have done so on a whimsy.
Israeli teen lightly wounded from stone throwing in West Bank settlement of Kiryat Arba (Haaretz)
from the article: Spoiling for a fight