touch
FilesPackage: coreutils
Creates an empty file, or updates an existing file's timestamp. The empty file that says "this script has run" or switches a rule on (/etc/cron.allow) is often made this way.
What its options do in the lessons
From the same glossary the lessons render under their commands, so the two cannot disagree.
touch -d- Sets the access and modification times to the date you name, written plainly. It is also what makes a modification time useless as evidence.