Use Google Classroom assign date
Google classroom assignments should show up in planbook for the day they are assigned. Give people the option to choose if they show up on the due date.
Lisa Urban shared this idea
Marion Creviston commented
Have Google Classroom assignments appear in Planbook on the date of assignment instead of the due date of the assignment.
Laura Walters commented
Exactly what I was just going to suggest.
currently the start and end dates for imported assignments are the due date for google classroom and they are both the same date