Cream butter; gradually add sugar, beating well. Add eggs, one at a time, beating well after each addition .
Combine flour and cocoa in a medium mixing bowl. Dissolve soda in buttermilk, and add to creamed mixture alternately with flour mixture, beginning and ending with flour mixture. Mix well after each addition. Stir in dates, pecans, vinegar, and vanilla .
Pour batter into 2 greased and floured 8 - inch round cake pans. Bake at 350° for 25 minutes or until a wooden pick inserted in center comes out clean. Cool in pans 10 minutes; remove layers from pans, and let cool completely. Spread Tutti-Frutti Filling between layers and on top of cake.