The automatic sorting will be done by looking at each pictures timestamp

The timestamp is saved in the pictures "exif" data

If a picture has been edited and saved it will have received a new timestamp and therefore it might not end up in the category you were expecting it to end up in

But there is an online free tool where you can:
  • Upload picture
  • Change the date of the exif data
  • Save it
  • and upload it again
You can find it here: