[curt.clifton]

You just set up your template so the project start or due date is set (or both) and all the item dates are set relative to that. When the script runs, if the project has a start or due date, the script will prompt you for the new start or due date. Then the script will automatically adjust all the item dates to maintain their relative "distance" from the project date.

So, you don't need to use the placeholders for dates. The placeholders are only for item titles.