Underground geek rock band names
Pyth
Encoder:
Jf-\'T'jdm@JdjswlJ

Takes two arguments: a dictionary on one line, and the date, in DDMMYYYY form on the next.
Filters out words with apostrophes from the dictionary, then converts the current date into a number with base equal to the dictionary length, and then chooses words from the filtered dictionary with indexes of the digits, and prints them out, space separated.
Today's result:
$ pyth -c &quot;Jf-\'T'jdm@JdjswlJ&quot; &lt;&lt;&lt; '/usr/share/dict/words
30102014'
Annam pals

Future results:
31102014
Antarctica economical

01112014
Abernathy carousels

02112014
Acadia unsnarled

03112014
Actaeon oversimplifying

04112014
Adela dugouts

0511204
Adolph Maude

To decode, run the date through the program and see if the output matches the name given. I'm not going to list any more band names, but from how the program works it should be clear there are no repeats.