Hi @AnnoyedMom -
I'm sorry to hear about your student's unneeded stress regarding coursework!
While there is no visible history of those changes, your student can subscribe to notifications regarding due dates. If this issue occurs for one course, I encourage you and your student to adjust the notifications for the single course. Otherwise, their notifications/inbox will be filled with additional noise that may become hard to track.
You can set the notification for Due Date under Course Activities to Immediately to track those changes. If you get the notifications through email, you'd have the timestamps to reference at a later date (if you need to!).
How do I manage my Canvas notification settings as a student?
How do I manage notifications for a single course as a student?
I hope this is helpful as you address the challenge.