The start date on all reports I run is defaulting to 01/01/19 instead of 01/09/18 please help.

This would indicate that the year start date has been amended to 23/04/19.  To amend this please go to Admin > Config > Core Set Up > School and edit the year start date here.  We would suggest adding this as the 03/09/18 so that the weekly breakdown still shows on the student profile in the attendance tab.  If this date is set as a weekend this will not show.