December 15th is generally the big day. I beg you to ensure early in the week that you have at the ready your logon id and password for your portal. There is nothing worse than having an admission decision, yet being unable to access said decision. Also, please keep in mind that as decisions are released, there will be students throughout the U.S. (and the world) attempting to access their decisions at both the same school and time as you. Have patience with the system, as it will likely be slow. But take a deep breath and calm those shaking hands.
Best of luck!