Preheat oven to 350 degrees F (175 degrees C). Grease and dust a 9x5-inch loaf pan with white sugar.
Combine dates, sugar, molasses, and butter in a large bowl. Pour tea over date mixture and mix well; set aside to cool, 15 to 20 minutes.
Whisk all-purpose flour, whole wheat flour, baking powder, cinnamon, ginger, cloves, salt, nutmeg, cardamom, and white pepper together in a bowl.
Stir egg and vanilla extract into cooled date mixture. Add 1/3 the flour mixture to the date mixture; mix well. Repeat 2 more times with remaining flour mixture until batter is just combined; fold in walnuts. Pour batter into the prepared loaf pan.
Bake in the preheated oven until a knife inserted in the middle of the bread comes out clean, about 1 1/4 hours. Cool in pan for 15 minutes before transferring to a wire rack to cool completely.
