Custody refers to a legal arrangement, while shared parenting responsibilities describe the actual activity between the adults. Often shared parenting, also called co-parenting, is interpreted to mean that parents are able to raise their children together, even if the parents are no longer marital partners. Cooperative and communicative parenting is optimal, but co-parenting can be effectively accomplished in less optimal circumstances, as long as parents can put aside their differences and focus on what the children need.
There are four types of post-divorce relationships between spouses: perfect pals, cooperative colleagues, angry associates and fiery foes (as a divorced father myself, I'd consider our son's mother and I in-between the first two!).
Two of the four types can create an effective co-parenting alliance. Bottom-line: successful co-parents communicate and negotiate with each other about the children, respect each other as parents despite their differences, put past issues aside and concentrate on the child, share control with each other and adopt a hands-off attitude toward how the other person parents, tolerate differences in child rearing practices and values without labeling them as harmful to the child and value what the other offers as a parent.
In those cases where our firm is contacted, then retained to create our client's agreement, I provide for "liberal and reasonable" access in between structured visitation so long as the parties can work together and the children are of an age where the flexibility works well. There are also all kinds of issues that can be written in an agreement. For example, if you feel that your time with the children is often reduced when they are sick, compensatory time will be scheduled if it is not too disruptive. Similarly, if your spouse hires a babysitter to watch the children when you would normally be available, you can specify that you get first right of refusal for extra time (most judges require a three or four hour period before this clause would kick-in).
For parents who want to share their children's time equally, there are many possible schedules. Some that are used frequently are every other week, every two weeks, Monday morning through Thursday morning and Thursday afternoon through Monday morning, Wednesday morning through Saturday morning and Saturday morning through Wednesday morning and September through June for summers for parents who live in different states.
The benefits of shared parenting accrue to both parents, as well as children. Some of the most salient advantages are the nonresidential parent is less likely to feel like a visitor and money-making machine; both parents feel good about their ability to work together for their children; the child has ongoing contact with both parents and both parents get more support for parenting. One of the best advantages when it all works out is how both parents get more support for parenting. When one needs help in a pinch, the other parent is more likely to step in and assist.