Preheat the oven to 350 degrees F (175 degrees C). Lightly grease an 8x4-inch loaf pan.

Grind 1/2 cup flax seed in an electric coffee grinder or food processor; set aside.

Beat together banana, oil, sugar, and eggs in a large bowl. Mix together flour, baking powder, baking soda, salt, ground flax seed, and 1/4 cup whole flax seed in a separate bowl. Gradually stir flour mixture into banana mixture. Fold in dates. Spoon batter into the prepared loaf pan.

Bake in the preheated oven until a toothpick inserted into the loaf comes out clean, 55 to 60 minutes.