Refactor code structure for improved readability and maintainability

frontend/src/lib/date-utils.ts

@@ -22,7 +22,9 @@ export function prepareDateForBackend(dateStr: string, timeStr: string = '00:00'
         // Combinar fecha y hora usando la zona horaria local
         const dateTime = toCalendarDateTime(date, time);
         const zonedDateTime = dateTime.toDate(localTimeZone);
-        return zonedDateTime.toISOString();
+        // Convertir a objeto Date nativo de JavaScript para obtener ISO string correcto
+        const jsDate = new Date(zonedDateTime.toString());
+        return jsDate.toISOString();
     } catch (e) {
         console.error('Error parsing date:', e);
         return null;