In a saucepan, combine dates, sugar and water. Cook, stirring frequently, until very thick. Stir in walnuts, if desired; cool. , Sift the flour, salt and baking soda together in a large bowl; add oats and brown sugar. Cut in butter until mixture is crumbly. Sprinkle water over mixture; stir lightly. Pat half into a greased 13x9-in. baking pan. Spread with date mixture; cover with remaining oat mixture and pat lightly. , Bake at 350° for 35-40 minutes or until lightly browned. Cool on a wire rack. Cut into bars.