When adding to-do's in your project templates you have the option of adding an offset to the project to-dos. For the project you also have the option to select wether the due date should relate to the project start or end date.
Examples:
Using the project start date
A task with a 3 day offset will set the due date of this task 3 days after the project start date.
Using the project end date
A task with a 3 day offset will set the due date of this task 3 days before the project end date.