Write down who covers the competing duties
If Robin wants Saturday from 10 to 11 for personal time, identify which shared responsibilities need coverage: the door, school messages, or an expected delivery. A calendar block with no coverage can leave Robin technically free but still fielding every interruption. Share only the information other people need to protect the block.
Negotiate the time before it becomes a standing arrangement
If both adults want Saturday morning, compare the constraints. One activity may have a fixed start, while the other could shift to Sunday without losing its value. Alternating weeks is useful if both can actually attend on the weeks they get. Do not promise a replacement slot that regularly conflicts with another responsibility.
Review what people really received
If both adults want the same time, alternate weeks or choose separate blocks. When an interruption removes most of a block, name a replacement time instead of writing it off. Review whether each person actually gets their time, not just whether it appears on the calendar.
After two or three weeks, ask whether each block happened and how often it was interrupted. If one adult's time disappeared because they still handled household messages, change the coverage rather than merely moving the event. A private label can stay broad even when coverage details need to be specific.