Treat the date as a planning objective while the underlying eligibility, evidence and process are reviewed. TN preparation and the government's actual decision are separate steps, and an anticipated date does not itself authorize work.
Identify what still needs to be confirmed
Ask what remains open before the support letter can be finalized, and who controls that missing information. Review the current admission procedures before booking irreversible travel. If the employer, duties or assignment changes, ask for a fresh review rather than assuming the original plan still applies.
Work backward from the last fact that could change the classification: finalized duties, a required credential record, the employer letter, or a changed client assignment. The first review should identify the owner of each open item and a date when it can be checked. Hypothetical example: a Canadian wildlife biologist is scheduled to begin a wetlands survey for a U.S.
conservation contractor after spring thaw, but the contract still names a different client entity. Correct the contracting record before booking travel, then recheck the support letter against the final assignment. A planned start date is useful only after the record is internally consistent; it does not itself permit the person to start working.