In » Schedule Display Settings, I have selected "Show the start and end time for every event". So that seems fine, except that the schedule groups presentations together based only on the start time (I have selected "Schedule presentations by time and date individually"). I have attached a screenshot to show the problem. The first few presentations in the 8:30 - 8:45 block are 15 talks, no problem, but the presentations at the end are part of a symposium that runs from 8:30 - 10:00.
Originally, we decided not to use time blocks because the conference organizer wanted the actual time to appear with each talk (ie. instead of having all talks listed under TALK SESSION 1 8:30 - 10:00 with no times, he wanted the schedule to say which talks start at 8:30, 8:45, etc.). In retrospect, I probably should've had them setup blocks for each talk time (ie. TALK SESSION 1.1, 8:30 - 8:45), but it's too late now - they've already spent a day entering presentations.
So, I think that this is a bug, that is, having a presentation that runs from 8:30 - 10:00 labelled as running from 8:30 - 8:45.