The requirement is that a student logs into moodle and when he starts the course, he has 'X' days to finish the course. This 'X' is a dynamic date which would be set based on when the student started the course.
In short, the student's course start date would dynamically define the course completion date. The course in general will never have a completion date as there will be a number of students enrolled to take the same course and each of them will have their own course completion date based on their course start date.
Can we achieve the above? We are on the latest Moodle 3.1.1.