fullcalendar/locales/es-us.js

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

  var esUs = {
    code: "es",
    week: {
      dow: 0, // Sunday is the first day of the week.
      doy: 6  // The week that contains Jan 1st is the first week of the year.
    },
    buttonText: {
      prev: "Ant",
      next: "Sig",
      today: "Hoy",
      month: "Mes",
      week: "Semana",
      day: "Día",
      list: "Agenda"
    },
    weekText: "Sm",
    allDayText: "Todo el día",
    moreLinkText: "más",
    noEventsText: "No hay eventos para mostrar"
  };

  return esUs;

}());