Looking at the ServiceDesk 7.1 SP2 SD.IncidentManagement project, Incident.DateCreated is filled with current date in 'Save Process ID and Tracking ID to Incident Submitted By and Date Created' component in Primary model.
The problem with this is that when an Incident is created from Technician Feeder, it is sent to CreateIncidentAdvanced model that never goes to The Primary model (it goes directly to Main Incident Work).
Where are your incidents created from?