Is the check in your office safe, or have you presented it at the bank for deposit?  From the tone of the question it seems you are still holding it, so the answer is NO. 

However, the UCC does permit the bank to accept the item and cash it before the date written on the instrument.  This is not mandated on the bank; the bank does not have to accept the check prior to the date written, but it can.

UCC § 4-401(c) A bank may charge against the account of a customer a check that is otherwise properly payable from the account, even though payment was made before the date of the check, unless the customer has given notice to the bank of the postdating describing the check with reasonable certainty. 

http://www.law.cornell.edu/ucc/4/article4.htm#s4-401