Preheat oven to 350ºF. Grease a 9x2" round cake pan.
In a large bowl, whisk together the flour, granulated sugar, baking powder, baking soda, salt and spices.
In a separate bowl, whisk together the pumpkin, brown sugar, oil and eggs.
Make a well in the dry ingredients, then add pumpkin mixture and gently fold together with a flexible spatula until just combined. Fold in dates, if using. Bake for 35-45 minutes, or until top springs back when gently pressed and tester inserted in the centre comes out nearly clean (a few moist crumbs are ok).
Cool for 10 minutes in pan before inverting on a wire rack to finish cooling completely prior to frosting.