Unless you're unhappy with your skin color, we strongly recommend avoiding tanning before your wedding day. Most brides end up with strap marks (which are impossible to photoshop in mosts), or even worse, we had some weddings when the groom had his sunglasses marked on his face from the sunburn.
If you decide to go for a tan, make sure that the uncovered parts on your wedding day will be even and most important of all, avoid at all costs looking red. If you look red from a tan, you'll look like a lobster in your wedding photos. Red is very difficult to eliminate from the skin because desaturating the reds in an image will make everybody else look extremely pale around you.
