In the new Hobbit movie, the warg riding orcs attack in daylight, which according to Tolkien's books should not be possible. Any speculations how this might be explained anyway? In the Lord of the Rings movies there were the Uruk Hai who could travel in daylight (as in the books). But these orcs seemed to be of a different kind.
Those were Hunter Orcs:
Or maybe this breed, like the Uruk-hai, can indeed withstand the sunlight better
(Because this is 'non-canon' there seems to be very limited information)