It seems not being of age to drink legally in the U.S. has been cramping his style, so he's been counting down the days until that's not an issue anymore.
Also? It's rumored his bandmates have been calling him 'Baby Spice.' 21 candles on this birthday cake oughta shut that one down. Maybe.
A source told the Daily Star: "Harry can't wait to be able to legally drink in the U.S. He's in arguably the most famous pop band in the world but still can't get a drink in certain places."
Crying a river over here, Hazza.
The insider added, "He's sick of being the butt of all the baby jokes in the group after being branded 'Baby Spice.'"
We'll be on the lookout for Harry to have an epic birthday bash - will all the 1D guys be there to celebrate with him?