Don't wear a tuxedo during the day.
First, a quiz. What's wrong with the picture to the right?
You guessed it: the groom is wearing a tuxedo — during the day.
For reasons that are still beyond all comprehension, the tuxedo has become the pinnacle of formalwear for the American man. Blame prom and pushy tuxedo-rental places.
But the tuxedo, which is commonly referred to as "black tie," was never intended to be worn while the sun was still up.
It didn't used to be this way. There was a time in the not-t0-distant past when men instead wore "morning suits" (the daytime equivalent of white tie) or strollers (the daytime equivalent of black tie) to their nuptials.
Both of these long-coated looks have fallen out of favor, supplanted by the less formal suit and tuxedo. The tides of history have turned, and for as long as we're living in these more casual times, men will be wearing suits and tuxes when they get married.
The most important thing to remember then is when it's appropriate to wear each of these two options. You should wear a charcoal suit when your wedding takes place during the daytime; and a black tuxedo when your wedding is in the evening. According to Articles of Manliness, the general rule of the thumb is that you dress for when the event ends, so any wedding that ends after dark is tuxedo-appropriate.
Though these rules are flexible (and, in some cases, may be bent until they're broken), the one critical guideline is that you must never wear a tuxedo in the daytime. As menswear blog PutThisOn says it: you'll look like a tool. Though the trend of men wearing tuxedos during the day is unlikely to stop, at least you can be confident that you're getting it right.
But if your bride-to-be insists that you wearing a tuxedo to the ceremony, it doesn't matter what time of day it is: you're wearing a tuxedo. Similarly, the dress code for an event during the day calls for black tie, don't show up in a suit.
If wearing a tuxedo during the day is improper, not following someone else's dress code wishes is just plain rude.