Parent and Child, and Series Events - Event Flow
It is possible for any event to be a parent event and have child events (sub events) linked to it. Events can be linked for 'reference only' or actually 'linked in time' and move with the parent event. The default link type is for 'reference only' but this can be changed in the event before saving.
Within the event window, on the flow tab, child events can be added directly to any event and the flow of events can be seen. The ID of the main event is added to any child events which creates the link. Any event with linked child events are automatically parent events.
To remove the link of child event from its parent you can edit the child event, click the Flow tab and change the Parent ID to zero. This will remove the link between the child event and its parent. The same can also be done to remove any event from a series of events, by changing the series ID to zero.
Also see this video /faq.php?q=10273(create, add, chain, linked, parent, child, events)