Grease and flour a 9x13-inch pan. In a large bowl combine sugar, flour, spices, and salt. Work in shortening as though for pie dough until the mixture resembles coarse crumbs. Remove and reserve 1 cup of crumbs for topping.
Add baking soda to buttermilk and stir into remaining mixture. Add dates and nuts while there are still a few dry lumps and continue stirring only until all is moistened.
Pour batter into pan, sprinkle with reserved crumbs, and bake in a 350 degrees F oven until top is browned and a toothpick comes out clean, about 50 minutes.