#!/bin/bash
while read -r dir
do
    echo "Checking dir '${dir}'..."
    last_file="${dir}/$(ls -ht -- "${dir}" | head -n1)"
    echo "Last modified file is '${last_file}'"
    touch -r "${last_file}" -- "${dir}"
done <<< "$(find . -mindepth 1 -maxdepth 1 -type d)"