Currently, when a discussion is imported from another Canvas course, the creation date and author info comes into the newly created course. For situations where course content is reused from year to year, it's very apparent to everyone how old the content is, and it's sometimes very confusing to students.
When a discussion is imported to a new course, the discussion creation date should either be updated to match the import date, removed entirely, or users need to have a way to update the date. Editing the discussion does *not* seem to affect the creation date.
Thanks for bringing this to our attention! I will bring this to the team, and we will be sure to include a better solution in a future release of the redesign.