This idea is called "Poor Man's Copyright" and is discussed by Snopes here: http://www.snopes.com/legal/postmark.asp http://www.snopes.com/legal/postmark.asp

This idea is called "Poor Man's Copyright" and is discussed by Snopes here: http://www.snopes.com/legal/postmark.asp http://www.snopes.com/legal/postmark.asp tl;dr Don't do that.