Lord of the Rings: The Return of the King - The Sun Is Rising in the North
Watch the scene were the Rohan army reach Minas Tirth, Now the army is to the North of the city, but the sun is rising right behind them, therefore, the sun is rising in the North, and not the East. The East is in the direction of Mordor.
"the east is in the direction of Mordor" You may or may not know this, depending on your familiarity with the Lord of the Rings books, but a cloud or atmospheric disturbance had spread from Mordor, darkening the skies. It would then make sense that the first light would show to the north and south, rather than to the east, which is the source of all the darkness.
If you watch.. i think it was the filming of.. something on the extended disc, they talk about this. Because of the big black shadow in the east, they had to have a light source from somewhere. So they actually have two suns (i didnt notice these but that's what they guys said) so that they could get the lighting right. Its still a slip up I guess if its noticable.. just thought you might find that interesting.