For the date filling; in a saucepan combine chopped dates, sugar, water and orange juice, bring to a boil and cook, stirring with wooden spoon over medium-low heat until mixture is thickened, pushing down with a fork or a potato masher to remove the large chunks and make the mixture semi-smooth, cooking time should take about 15-20 minutes)set aside.
For the crust; in a large bowl combine the cake mix with oatmeal, cinnamon and brown sugar.
In a small bowl whisk together melted butter with egg and vanilla; add to the flour mixture; using clean hands mix with fingers until the mixture barely holds together.
Measure out two-thirds of the mixture and pat into the bottom of prepared baking dish, pressing down with hands to cover evenly.
Carefully spread the prepared date mixture over the bottom crust, spreading out to cover the pan.
Cover the top with remaining oat mixture and gently pat the mixture down slightly with hands (do not pat down to much!).
Bake for about 20 minutes (the top should be very light brown).
Cool completely or semi-freeze before cutting (this will make slicing the bars easier).