When you create an assignment, by default each assignment is assigned to everyone. However, the assignment can be differentiated among course sections, course groups, or individual students.
When grading periods are enabled, the due date of the assignment determines the grading period where the assignment appears in the Gradebook. If no due date is set, the assignment defaults to the last grading period available for the course.
When grading periods are weighted, assignments outside of grading periods do not count toward the final grade.
Note: The Assign field cannot be edited for anyone if the due date is in a closed grading period. However, you can add additional differentiated assignments with due dates outside the closed grading period. Assignments with due dates in open grading periods cannot be edited from an open grading period to a date in a closed grading period, but the due date can be edited to any date within an open grading period. These restrictions do not apply to availability dates, which can be set to overlap a grading period.