This can be frustrating, but try to think about the reasons the other parent is late. For example, does he or she work late on certain days? Is the traffic bad on the way to your house? Are there transportation issues? Does he or she feel uncomfortable coming to your house when your new girlfriend or boyfriend is there?
Most of these problems can be worked out by having a conversation about the problem and how to address it. For example, have your child ready for pick up one hour later than the order says or just quietly have things ready in case the parent shows up.
You and the other parent can agree to any parenting time schedule that works for both of you.
For help coming to an agreement, read about mediation and mediation alternatives.