Does Dropbox Keep Photo Dates?
Dropbox stores the file unchanged, so the photo's own date survives. The file date on your disk may not.
Dropbox syncs the file as it is. The date inside the photo comes through untouched. Its own timeline view reads that date, which is why Dropbox usually shows the right one even when your file manager does not.
The file dates on disk are another matter. A fresh sync to a new computer writes the files today, so Created and Modified are today. The photo is fine; the file dates are not.
Sort by the photo's own date, and fill it in where it is blank. Takeout JSON Metadata Fixer handles the blanks. It runs on your own computer and is free for your first 500 photos.