Preheat oven to 350F & grease a Swiss roll tin. Put the margarine, sugar & molasses into a thick pan & heat very gently until the fat is melted, stirring well. Stir in the oats, dates & the spices. Press the mixture into the prepared tin. Press flat & bake for 25 minutes. Cool in the tin for 15 minutes. Score into squares with a sharp knife. Leave in the tin until completely cold & then cut into pieces to serve.