The link provided will send you to the accepted legal decision making and parenting plans ( custody ) for your location. Complete all required paperwork: • Petition to Modify (the Petition).Requesting legal decision-making and parenting time ( custody ) can take place at any time in Arizona. The first thing to do is to complete the court forms. In Arizona, a child custody establishment case takes at least three months but can take up to a year and sometimes even longer. Court Forms and Instructions. Completing the Forms. Court for a change of parenting time and child support. Read it carefully before you fill out the Petition. 1. I agree with both answers above.