The previous arrow is for some reason undersized on OSX Chrome 25.0.1364.160 and Safari 6.0.2. This does not seem to be the case when the fullcalendar library is used independently of the fullcalendar Drupal module.

UI still works--just looks a little funny:

Previous arrow misaligned in OSX

Screen Shot 2013-03-11 at 9.07.04 AM.png10.79 KBMirabuck