Canvas updated the "Assign To" functionality recently to include module items and pages. While a very welcome change, I am frequently encountering an issue where I cannot assign items with "Until" deadlines on the same day as the "Due Date" without jumping through an extensive number of hoops. This is because Canvas is reporting them as AFTER the due date and returning the error "Lock date cannot be before due date", despite that not being the case:

This appears to happen every time a new "Due Date" is created as Canvas assumes the "Due Date" is 11:59 PM by default (or w/e default time is set on the Canvas) or if a "Due Date" was saved earlier, it will use that. To add a same-day Until date to an assignment, I have to jump through some hoops:
- Create and save the correct "Due Date".
- Double check the date did not default to 11:59 PM. Click out of the interface seems to reset to the default time even if a time has already been entered.
- Reload the page and re-open "Assign To" to refresh the "Due Date"
- Add the new "Assign To" time.
- Reload the page and confirm all the times again.
Changing the default time to much earlier in the day mitigates this, as the "Assign To" time is less likely to occur before say, an 8 am default time than an 11:59 default time. I also frequently see the course default time re-insert itself into boxes I had thought I had correctly edited. I will submit a separate issue for that...
The behavior I expect to see is that I can edit all of the submission boxes at once, rather than having to update them in sequence.