They can update their tentative occupancy date any number of time as long as it falls under your outside occupancy date. What is your outside occupancy date? Amendment will happen if there is any change in the outside occupancy date. There is no amendment for change in tentative occupancy dates, it will be just an email notification.
For eg: in my case first tentative occupancy date was Dec, 2020, when I signed contract. Later on they changed that dates so many time, I lost count of that. But my outside occupancy date is April 2025. They can't complete the project before that. Hence they need to amend this outside occupancy date for my agreement. When they do that, we have choice to get out of the project or stay with the latest outside occupancy date.