touch -r

touch -r *(Dom[1]) .
touch -r **/*(Dom[1]) .

touch -r "$(find -mindepth 1 -maxdepth 1 -printf '%T+=%pn' |
            sort |tail -n 1 | cut -d= -f2-)" .
touch -r "$(find -mindepth 1 -printf '%T+=%pn' |
            sort |tail -n 1 | cut -d= -f2-)" .

mostrecent="`stat -c '%Y %n' * | sort -n | tail -n1 | cut -d ' ' -f '2-'`"

mostrecent="`ls -t | head -n1`"

touch -r "$mostrecent" *

touch -r "`ls -t | head -n1`" *

#!/bin/bash
if [ -z "$1" ] ; then
  echo 'ERROR: Parameter missing. specify the folder!'
  exit
fi
#MODE=tail # change to newest file
MODE=head # change to oldest file
for d in "$1"/*/; do
  echo "running on $d"
  find "$d" -type d -execdir
    echo touch --reference="$(find "$d" -mindepth 1 -maxdepth 1 -printf '%T+=%pn'
                              | sort | "$MODE" -n 1 | cut -d= -f2-)" "$d" ;
    # remove echo to really run it
done

mkdir /tmp/test
cd /tmp/test
mkdir d1
mkdir d2
touch d1/text1.txt
sleep 1
touch d1/movie1.mov
touch d2/movie2.mov
sleep 1
touch d2/text2.txt
touch notthis.file