emulate Linux's `last -x` on Mac OS X
Is the following sufficient?

uname -a
Darwin Macmini-i53.local 13.0.0 Darwin Kernel Version 13.0.0: Thu Sep 19 22:22:27 PDT 2013; root:xnu-2422.1.72~6/RELEASE_X86_64 x86_64

last | grep -e boot -e shut
reboot    ~                         Mon Dec  2 09:57 
shutdown  ~                         Mon Dec  2 09:54 
reboot    ~                         Fri Nov 29 12:45 
shutdown  ~                         Fri Nov 29 12:40