Interesting how different Linux desktops cater (or not) for "I don't want to see the clock on the screen".
MATE -> Right click, remove
Unity -> Tickbox in settings
GNOME Shell -> You can't. Write an extension
elementaryOS -> Uninstall a Debian package
@popey that UX argument of hiding all of the clutter and settings for the user not to be overwhelmed is just ludicrous; there should always be a balance, and I think unity did that pretty well.