Britney, 39 years old on December 2, 2013, celebrated Her birthday during rehearsals at Her new Planet Hollywood Show. The show entitled “Piece of Me” is showing at Planet Hollywood Theater Of The Performing Arts in Las Vegas, NV. Now 39 years old, Britney has turned out to be a great Mother and a very responsible workaholic. What a difference 10 years can make. You might be surprised at how good this show is going to be.