Thank you. Although I do have a MacBook, I mostly use my iPad and iPhone with Evernote. Consequently, I hadn't realised it was possible to change the dates in the desktop version. I've just done that for one notebook, and now it gives me exactly what I wanted in terms of a view sorted by original date. I can chip away at this over time to one-time correct other notebooks.
I'm sure I'll try the other tips for other purposes too at some point.
Thanks again for the helpful reply!