I’m posting this because I got a sunburn on the beach in late August and searched desperately for a way on how to fix them before my wedding which is on October 29th. I figured someone might have the same issue at some point so here is what helped me:
1) I tried two different treatments to make the tan lines go away. The first treatment was baking soda with a little water in it to make a paste. Rub it on your lines, wait 15 minutes, and wash off. The second I tried was fresh lemon juice mixed with honey. Leave on for 25 minutes then wash it off. The treatment I tried depended on what I had around my house that day. 
After doing that once (sometimes twice) a day, the lines went away after about 3 weeks!
2) I also used Jergens Natural Glow directly on the untanned parts of my skin. Gave me a nice glow and helped those areas match the tanner areas better.
Hope this helps another bride to be!
