Lost profits arising from the injury of a principal employee or owner require an analysis of the actual and ‘but-for’  revenue of the business entity.  The date(s) the alleged economic damage to the business began and end is an obvious stating point in the business damages analysis.
Generally, there may be multiple dates if the economic damage occurred in stages.  For example, there may be a major impact time period, such as a period of time where principal(s) or the owner were not able to perform any managerial duties at all following a physical injury.  Following the major impact period, the principal(s) or owner may have returned to their duties in a limited capacity or full capacity after some amount of time