Sprinkle soda over dates; add water, and set aside.
Cream butter; gradually add sugar, beating well. Add date mixture and egg; beat well.
Combine 1 3/4 cups flour, baking powder, and salt; add to creamed mixture, beating until smooth. Dredge pecans in remaining flour; stir into batter. Stir in vanilla.
Spoon batter into a greased and waxed paper-lined 9- x 5- x 3-inch loaf pan. Bake at 350° for 1 hour and 5 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 10 minutes; remove from pan, and cool completely on wire rack. Slice, and serve with cream cheese, if desired.