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 the majority of the time as the custodian of the child. However, this designation shall not affect either parent’s rights and responsibilities under a parenting plan. In the absence of such a designation, the parent with whom the child is scheduled to reside the majority of the time is considered to be the custodian of the child for the purposes of such federal and state statutes. When a court orders that custodial allocation shall be on an equal (50-50) basis, the court shall also specify in its order which parent may claim state and federal income tax deductions and exemptions for the child or children: Provided, That such claims to state and federal income tax deductions and exemptions for the child or children may be divided equitably between the parents, year to year.