This is a useful little trick to use in your scripts – particularly for things like periodic backups.
For a file:
touch $(date +%F)
creates the file 2012-11-18
For a folder, let’s add the time after the date:
mkdir $(date +%F-%H:%M)
creates the folder 2012-11-18-09:00
We can use this in a command, like so:
tar -cf $(date +%F).tar /path/to/files/
This creates the tarball (archive) file 2012-11-18.tar from the files in the /path/to/files/.
To see the other options, type man date or visit the Ubuntu webpage on date here