Solely for the purposes of all other state and federal statutes which require a designation or determination of custody, a parenting plan shall designate the parent with whom the child is scheduled to reside a majority of the time as the custodian of the child. However, this designation shall not affect either parent's rights and responsibilities under the parenting plan. In the absence of such a designation, the parent with whom the child is scheduled to reside the majority of the time shall be deemed to be the custodian of the child for the purposes of such federal and state statutes.