How to enable Time Machine to backup to network disk

Easy. Just follow these steps:

 sudo defaults write TMShowUnsupportedNetworkVolumes 1
  1. Obviously you need another Mac to which you want to backup to, with the disk formatted as Mac OS Extended Journaled.
  2. Open Terminal from Mac you want to backup from. Issue command
  3. Open System Preferences → Time Machine. Click Change Disk. Your network disk should appear now.
  4. Select it, and you are good to go.