If you bought the WD for Mac, I'm assuming that the disk formatting is 'Mac OS Extended (Journaled)', but to check simply open Disk Utility (in Applications or from Launchpad -> Other) and highlight the external HD, then look the bottom (see my screen capture of my Seagate external HD, blue arrow) - this drive is my Time Machine MBPro BU (I have the same early 2013 laptop).
Just wondering but w/ an early 2013 MBPro, why have you not upgraded to Yosemite (10.10.1)? Of course, your issue could be corrected w/ a change of OS X? Click to expand.Hi again Sue - thanks for the additional information.
