If you set a field like date: YYYY-MM-DD in your files, you’ll be able to use dataview (and other plugins which respect this field similarily) with file.day or similar. This will indeed allow you to do view for stuff like a year ago, 90 days ago, and so on
Doesn’t the Day One file have a created field you can utilise? I kind of remember that I did that when I converted most of my entries some time ago.
Regarding how to do this automatically, I can say it’s doable, but it can be tricky and depends on your knowledge of coding and/or doing regex stuff on multiple files. For most people it’s easier and safer, to just do it manually, as you’re converting the files.
If not using the Day One field, from where are you going to pick the creation date from?