Here are some useful hints about how to use find in Linux.

find /path/to/dir/ -type d -exec chmod 0755 {} \;
find /path/to/dir/ -type f -exec chmod 0644 {} \;

find /path/to/dir/ -newermt "2013-01-01 00:00:00" ! -newermt "2013-01-02 00:00:00"

[OR]

touch --date "2018-07-01" /tmp/start
touch --date "2018-08-01" /tmp/end
find /path/to/dir/ -type f -newer /tmp/start -not -newer /tmp/end