A valid entrustment agreement terminating all parental rights and responsibilities to the child shall be revocable by either of the birth parents until (i) the child has reached the age of 10 days and (ii) seven days have elapsed from the date of execution of the agreement. In addition, a valid entrustment agreement shall be revocable by either of the birth parents if the child has not been placed in the physical custody of the prospective adoptive parents at the time of such revocation. Revocation of an entrustment agreement shall be in writing and signed by the revoking party. The written revocation shall be delivered to the child-placing agency or local board to which the child was originally entrusted. Delivery of the written revocation shall be made during the business day of the child-placing agency or local board to which the child was originally entrusted, in accordance with the applicable time period set out in this section. If the revocation period expires on a Saturday, Sunday, legal holiday or any day on which the agency or local board is officially closed, the revocation period shall be extended to the next day that is not a Saturday, Sunday, legal holiday or other day on which the agency or local board is officially closed. Upon revocation of the entrustment agreement, the child shall be returned to the parent revoking the agreement.