The following steps illustrate how to include the Timestamp task in a Project, and then use the date variable to prefix files retrieved from a FTP server:
Create a new Project or edit an existing Project.
From within the Project Designer page, expand the Miscellaneous folder in the Component Library, and then drag the Timestamp task to the Project Outline.
The Timestamp task opens. You can optionally specify a Label, which would be shown in the Project outline.