Preheat oven to 400°F (200°C). Line a 12-cup muffin pan with paper liners, or grease the cups using a cooking spray with flour.
In a large bowl, whisk together the flour, brown sugar, baking powder, baking soda, cinnamon, nutmeg, salt, and orange zest. Make a well in the center.
In a separate bowl, stir together the butter, milk, eggs, and orange juice. Add to the flour mixture, and stir just until combined. Stir in the dates and nuts. If you like, save some nuts to top off the muffins.
Divide the batter evenly among the muffin cups, using about 3 tablespoons of batter to fill each about 3/4 full. Sprinkle any reserved nuts and a pinch of coarse sugar on top of each muffin if you like.
Bake 16 to 20 minutes, or until a pick inserted into the center comes out clean.
Cool in the pan on a wire rack for 10 minutes. Then transfer the muffins to a wire rack to cool completely.
Notes
Store in an airtight container at room temperature up to 3 days.