Find all photos without date information
$ exiftool -filename -filemodifydate -createdate -r -if '(not $datetimeoriginal) and $filetype eq "JPEG"' .
Set last created and modified to a specific date
$ find . -name "*.jpg" | while read filename; exiftool "-AllDates=1986:11:05 12:00:00" "$filename"; done
Copy of the originals will be created. Remove *.jpg_original if everything went fine or add -overwrite_original parameter.
Timeshift
by one year
$ exiftool "-AllDates+=1:0:0 00:00:00" .
Rename your files to contain the date and time
they will be suffixed with -N if they have the same date and time
$ exiftool '-FileName<DateTimeOriginal' -d "%Y%m%d_%H%M%S%%-c.%%e" *.jpg $ exiftool '-FileName<DateTimeOriginal' -d "%Y-%m-%d %H.%M.%S%%-c.%%e" *.jpg
Copy your photos in a folder structure organised by datetime
exiftool '-Directory<CreateDate' -d ~/Dropbox/Photos/%Y/%y%m -r .