It appears that only 'normal' tasks are displayed in the calendar. Sub-tasks and sections, even though they can be assigned dates, will not show up in calendars.
This is more a feature request, but I figure this is the best place for it.
EDIT:
It appears that the team calendar does not have sections, even when they are assigned to people in the team. It also does not have sub-tasks.
The per-project calendar does have sections, but does not have sub-tasks.
Sub-tasks don't appear in the per-project or team calendars, but they DO show up in the all-tasks calendar. The all-tasks calendar does not have sections...
I think we just need consistent task inclusion across all calendars.
Generally, the admins of StackOverflow tend to delete questions not related to programming. If you want to make feature suggestions, support is generally the best place to do so - they also collate feature requests and make sure the ones that are frequently requested bubble up.