How long does it take to master body language ?

Body language is something that you already know, You just don't realize it. How do you know with out asking that someone is angry if they haven't said any thing to you??? Their body language, the way that they walk and the way that they stand and hold their hands. You already know a lot about body language, You just have to take what you know and to apply it. Look at people and try and see what they are telling you before you engage them in conversation. Watch people around you and see what you can guess from the way that they are walking and moving and saying things with out saying any thing. You'll find out that you know more than you think.