Account and Event Administrators can set times for each submission within a session when you create/edit a session.

Click the 'Schedule individually' checkbox in the 'Submissions' area of the create/edit Session screen.

Enter the ID number of each submission(s) you wish to include in the timeframe within the session then enter the relevant start and end times.  You can schedule individual or multiple submissions in each timeframe.  Click 'Add New Time' to add each new timeframe into the session.

Click 'Save' when you have finished adding all the individual sessions.

When you preview/publish the programme, the individual times for each submission are displayed when you click on the relevant session.