Though there are some old-school etiquette rules that still stand -- yes, tails are still too formal for daytime -- when it comes to a casual celebration, any time of day is fine. Just because your ceremony will be in the evening doesn't mean it must be black-tie. You can clue guests in to the formality of your wedding with your save-the-dates and invitations. Don't include explicit wardrobe info; instead, pick a style that reflects the spirit of your event (if you're thinking casual, engraved script on ivory probably isn't for you). You might include wardrobe info elsewhere however -- for example, many couples include that kind of info on their wedding web pages (to make your own, go to TheKnot.com/weddingwebpage). And of course, make sure your family, attendants, and close friends know -- that way, they can spread the word for you.