In the course settings, it is possible to set the course end date prior to the course start date. It seems that this should not be permitted. Or, at a minimum, a warning icon should appear alerting the user making manual changes to the course settings that this has occurred. Many schools manually copy course content in from other courses - including the settings. The instructor then updates the course start date, but fails to update the course end date, which results in the course end date being prior to the start date.
The potential impact of this is that if the 'only allow users to participate between these dates' option is checked in the course settings, an instructor may unintentionally block students from accessing the course and/or conclude the course based on the end date.