It's a good point actually, In the Forgotten Realms, goblins aren't really known for being diurnal. They have darkvision, lair in caves, and are traditional night raiders. Goblins don't have agriculture, they scavenge food from the surroundings, and steal from or raid other lairs or small villages of other races in the vicinity. A daylight attack against a fortified grove filled with druids seems out of character. They know that they have better night vision than humans, and in fact have worse vision in the light.