How long will it take for my sun burn to turn into a tan?

Kay me and my friends went tanning, and basically i look like a giant red popsicle aha, with the worst tan lines *ever *. So basic, how long will it take for it to fade/ turn into a tan ( When my skin burns, it tans iunno why ) Soo yeah :) Even if your not sure, your opinion and experience would be appreciated because i'm playin a concert in a week.. and i cannot look like this Thanks :) !