change calendar locale to match site language.

footer-scripts.html

<script>

(function() {
    const locale = (document.documentElement.lang || 'en').toLowerCase();
    
    if (locale === 'en' || typeof FullCalendar === 'undefined') return;
    
    // Store original Calendar constructor
    const OriginalCalendar = FullCalendar.Calendar;
    
    // Override Calendar constructor
    FullCalendar.Calendar = function(element, options) {
        // Inject locale into options
        options = options || {};
        if (!options.locale) {
            options.locale = locale;
        }
        
        // Call original constructor
        return new OriginalCalendar(element, options);
    };
    
    // Copy static properties
    Object.setPrototypeOf(FullCalendar.Calendar, OriginalCalendar);
    FullCalendar.Calendar.prototype = OriginalCalendar.prototype;
})();
  
</script>