This post was published 4 years 2 months 30 days ago. Therefore, it may well be out of date. Do not reply on the contents of this post being accurate. Volker’s posted Time Machine: How to backup to unsupported volumes. Copy & paste one line into Terminal and your done. Very nice.
But, don’t use this method to backup to an AirPort Extreme AirDisk. For more info read what Michael Long from iSights.org has to say.