Your statement in the first paragraph is correct. Of course in between the charter and negotiating the actual finish date, there will need to be planning with the project team.
The last finish date is part of the baseline, however if you approach the project from a holistic viewpoint, the entire approved schedule is the baseline and you will track all differences from it. This will provide valuable information about estimates and actuals which can be used in future projects. It will also aid you in keeping that final deliverable date if you can identify and address the roadblocks.