Paternal Leave

I have just read a joke on a magazine. It is in Chinese and I have made it into English here with a few changes:

Soldier: I would like to take a few weeks off to take care of the baby my wife is having, Sir.

Sergeant: Sure. Go for it.

After the soldier come back to work the Sergeant asked about the new-born baby and the mother.

Soldier: Don't be ridiculous. It's gotta be 9 months before the baby is born, Sir.