I can't reproduce that behavior. Perhaps you're mixing up the Sent date that
the default activities view shows with the actual Start date for the event?
The Sent date shows when a calendar item was created.
To see the Start date for appointments, right-click the column headings in
the activities list, choose Field Chooser, switch the list of fields to All
Appointment Fields, and drag the Start field to the column headings. You can
do the same thing with the Start Date or Due Date field from All Task
Fields. Unfortunately, these changes affect only the current contact.
Outlook provides no way to apply them to the Activities tab in every
contact.