I may have asked a version of this question before, but it appears default load data provided by SAM does not align with start time defined by SAM help docs. Feb 2018 page 742 says SAM assumes January first is a Monday. Default load data I've pulled from SAM does not show a weekday (Monday) load until after 24 hours, suggesting SAM assumes January first is really a Sunday.
I apologize if this question has already been answered.