You may wish to check the validity of which files are chosen as your find is looking at the modified time information whereas the ls is looking at the change status time ... maybe they are similar
but it probably doesn't hurt to confirm you are still dealing with the correct files
I would add, $() is a much clearer way of performing substitution than `` and has the advantage of being able to be easily nested should the need arise (not an issue here of course)
Also, whilst we got there with a one liner, some times it can be clearer in the future to use a script which can be commented instead of relying on one's
memory to regurgitate difficult one liners ... just at thought