if($('#widget-calendar-body')[0]) {
    var calendarEl = document.getElementById('calendar');

    var calendar = new FullCalendar.Calendar(calendarEl, {
        plugins: [ 'interaction', 'dayGrid' ],
        timeZone: 'UTC',
        defaultView: 'dayGridMonth',
        header: {
            left: 'prev,next today',
            center: 'title',
            right: 'dayGridMonth,dayGridWeek,dayGridDay'
        },
        editable: true,
    });

  calendar.render();
}