Ubuntu: How to create a file or folder using today’s date

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.