These docs are for an old release. Info on upgrading to version 2/3
edit doc

buttonText 1.3

Text that will be displayed on buttons of the header.

Object, default:

{
  prev:     '&lsaquo;', // <
  next:     '&rsaquo;', // >
  prevYear: '&laquo;',  // <<
  nextYear: '&raquo;',  // >>
  today:    'today',
  month:    'month',
  week:     'week',
  day:      'day'
}

If you wanted to change the prev/next buttons to use < and > characters, here is what you would do:

$('#calendar').fullCalendar({
  buttonText: {
    prev: '&lt;',
    next: '&gt;'
  }
});