Velocity is completely space-preserving -- that is, the line break does exist in the HTML version, but HTML swallows up line breaks and you don't see it in the rendered output (because it's not an HTML break, <br>).
To suppress empty lines, you can wrap what are called void methods in a #set:
#set( $void = $calNow.add($calConst.DATE,6) )
Thank you!!