For the filling, in a medium saucepan combine pitted dates, raisins, and 1 1/2 cups water. Bring to boiling; reduce heat. Simmer, covered, for 8 to 10 minutes or until thickened. Set aside to cool slightly.
Meanwhile, in a large mixing bowl beat the butter with an electric mixer on medium to high speed for 30 seconds. Add the brown sugar; beat until combined. Beat in the flour, baking soda, and salt until crumbly. Stir in the oats and 1 tablespoon water until combined. Press half of the mixture into the bottom of a 13x9x2-inch baking pan.
Spread the filling evenly over mixture in pan. Sprinkle filling evenly with remaining crumb mixture, pressing slightly into filling. Bake in a 350 degree F oven about 35 minutes or until golden. Cool in pan on a wire rack. Cut into bars. Makes 32 bars.