Make the repeating pattern visible
Start with the regular weekly pattern, then add school breaks, holidays, birthdays, appointments, and travel arrangements.
A shared calendar gives both households the same reference point and makes upcoming handoffs easier to review.
Plan for changes
Agree on how much notice is normally needed for a change and use a structured request when the proposed change affects the other parent.
Keep the original event and the agreed change clear so the history does not depend on memory or scattered messages.