Although there isn't a way for users to check this from their own accounts, members that are apart of a business group can request this information from their group administrators. This information would be in the business group reports your Administrator receives/can generate at any time.
Please reach out to your group admin who would be able to provide you with information on when you started/completed a course.
If you're unable to locate anyone within your company, please reach out to DataCamp Support. firstname.lastname@example.org can certainly pass this request along to the Administrators of the Group, who would then be in touch as they see fit pertaining to your request.