Old enough.

When the girls are naughty, they go into a corner where we have a little time out stepstool they have to sit on there on the timeout.  Once they are allowed out of the corner, they have to give a hug to apologize to whomever they wronged.  This is Delilah's first time in the timeout corner.  She hit me when I was trying to help her brush her teeth.  

Ahhhh... First haircut, first timeout... These milestones come so quickly.