When a module or assignment is assigned to students, course sections, or groups, and these assignments overlap for an individual, Canvas uses an order of precedence based on the set_type to determine their due date. This order is shown in the chart below.
To learn more about assignment overrides, refer to the Assignments API article in Canvas LMS - REST API and Extensions Documentation.
Modules
Individual Student (aka ADHOC)
↓
Hidden Group
↓
Course Section
↓
Everyone
Assignments
Individual Student (aka ADHOC)
↓
Collaborative Group*
↓
Hidden Group*
↓
Course Section
↓
Everyone
*Since an assignment cannot be assigned to both collaborative and hidden group, it is safe to combine these two, rather than treating them as separate precedence rules.
This resource document can also be accessed from the How do I assign an assignment to everyone, individual students, differentiated tags, or sections? guide.