Negotiable Instruments Law
Section 13. When date may be inserted.-Where an instrument expressed to be payable at a fixed period after date is issued undated, or where the acceptance of an instrument payable at a fixed period after sight is undated, any holder may insert therein the true date of issue or acceptance, and the instrument shall be payable accordingly. The insertion of a wrong date does not avoid the instrument in the hands of a subsequent holder in due course; but as to him, the date so inserted is to be regarded as the true date.