Organizing images by date

Thanks for all the help and good answers. I got to thinking about all the collections I've made, both manual and smart albums, and I was afraid I'd destroy a lot of them if I deleted photos and re-imported. Maybe the smart albums would "survive" but not the manual ones. So I took no chances and set about doing the whole job manually, as I was first advised. Thanks to LR's incredibly good sorting options in the library module, the job goes very quickly once you have found the right way to do it. I'm already well underway, and at the same time I get to clean up the library in a way I wouldn't have been able to do otherwise.

You can reimport them, and have LR organize by date during the reimport process. This is possible if the photos have capture dates in the metadata.

To be careful and sure you don't lose anything, I would suggest importing them into a new catalog, using Lightroom's organization feature while importing... and verifying all your edits and any other data are included with the images. Once the new catalog looks to be structured properly with the correct folder organization, you can go to your original catalog and remove the older non-organized images, and "Import from catalog" to bring in the freshly organized ones.

Note that when you remove the older non organized images from your original catalog, I would leave them on disk until you're sure you've gotten everything in place and verified.

Is there a way to get images organized like this after they are imported?

Manually

Better yet, leave the images in their current folders, despite the fact that the folders are not yyyy/mm/dd, and from this point on, organize and search using keywords and other metadata. You can use the Filter bar in Lightroom Classic to find photos taken on any particular date, regardless of the folder name.