Actually a morning coat is proper for any formal daytime occasion, such as a garden party, afternoon tea, or luncheon. It is NOT to be worn at night, no matter how handsome the bride thinks the groomsmen look in it (and daytime weddings, with a wedding breakfast, are more formal than ones held in the evening, anyway, but few people know this). Unfortunately, the only men who own morning coats anymore are in diplomatic circles, and even this is fast fading into memory...