Open an event, appointment or task and use the Comments section. Comments are useful for notes such as “I’ll pick her up” or “Remember the costume”.
Anyone who can view the shared calendar item can add a comment.
If you move one occurrence of a repeating task to a different date, its occurrence discussion follows that moved item. This includes one-year birthday or occasion preparation-task exceptions.
If you correct the parent birthday/occasion date, the matching preparation-task discussion moves with the recalculated occurrence. If you split a birthday with This and future occurrences, its future preparation tasks, statuses and occurrence discussions follow the new future series while earlier history stays with the old one.