I have a document that has April 1, 2011 - March 1, 2011. It was initaled at the very bottom of Contract. I had to go back and look at the document

The first question is the type of document.  Generally, interlineated initials are used so there is no confusion as to the change.  Here, the intent is somewhat clear:  something was to happen for eleven (or twelve) months.  Writing 2012 over the contract usually doesn't make it unenforceable.  You may have to have a judge determine the intent of the parties, but that is usually the only issue.  Having a mistake in a contract isn't all that unusual, and the court may have to decide what was intended.  The law is not as rigid as you would suggest. The parties' course of conduct and the other terms of the contract, as well as other things are evidence of what the parties intended.  It is the intent of the parties that prevails in law as a general proposition.