Kalvid Assignment Timeline Due Dates not updated on edit #461
Description
When creating a new Kalvid Assign you can assign a due date.
After saving this appears in the student Timeline block and the Calendar.
If you update the Kalvid Assignment to change the due date, the calendar event gets it's "timestart" updated based on the new time it's due but not it's "timesort". This means it appears with the new time correctly in the Calendar, but still shows in the same old location in the Timeline view.
I think this is a standalone issue but there's an error in almost the same code for updating existing events about expecting only one event to be associated with each Assignment, which isn't true with the new completion reminder event and causes an error. I'll file a separate bug for that, as I don't think one causes the other.