teacher can not change Due date after an assignment is expire???

[vinhnq]

my teachers told me that: they are can not change due date after an assignment expired???

why? who can tell me please!

[James]

 @vinhnq  

Are you using grading periods? In Canvas Release: Close Dates for Grading Periods (2017-01-28) , there's a note at the top that says "Instructors cannot edit any assignments with due dates in a closed grading period."