ctrlpanel/public/plugins/fullcalendar/locales/en-nz.js

FullCalendar.globalLocales.push(function () {
  'use strict';

  var enNz = {
    code: 'en-nz',
    week: {
      dow: 1, // Monday is the first day of the week.
      doy: 4, // The week that contains Jan 4th is the first week of the year.
    },
  };

  return enNz;

}());