North lines...

To rotate to True North, have a floor plan open (eg):

• Draw a line which represents true north on the plan somewhere
• View Properties, Orientation, change from the default of "Project North" to "True North"
• Manage, Position, Rotate True North - then select 'place' on the options bar ribbon, trace along  your new North line THEN move straight up (ie. North) and click...
• This is now 'True North' (Project North is now just for Sheet placement)
• Now Revit will show shadows in the correct position REGARDLESS of whether you have the setting in Properties