I think your assumptions are pretty close. Keep in mind, however, that Microsoft Project uses the Project Calendar (set in the Project Information dialog) to calculate the schedule of every task in the project BEFORE you assign resources. When you assign resources to a task, the schedule shown on their Resource Calendars will control the schedule of the task. To completely override the Project Calendar (task has no resources assigned) or the Resource Calendars (task has resources assigned), you can use a Task Calendar. Hope this helps.