When to mail cards

Hi Everyone,, I have Christmas cards that have to go to different countries. Does anyone know when the mailing deadlines are yet?? I need to send some to Scotland, England, and Canada. I started filling the out about a month ago,,, good thing to do while you are waiting at the doctors, riding in the car, while hubby drives, any time you are just sitting waiting with bored hands. Thanks, Trudy In Missouri