fix enrollment for the new school-year

public/assets/js/modal_validation.js

@@ -8,12 +8,28 @@ document.addEventListener('DOMContentLoaded', () => {
   const gradeRE = /^[A-Za-z0-9\s-]{1,20}$/;
   const MIN_AGE = 5, MAX_AGE = 18;
 
+  const parseDateOnly = (value) => {
+    const match = String(value || '').match(/^(\d{4})-(\d{2})-(\d{2})$/);
+    if (!match) return new Date(NaN);
+    return new Date(Date.UTC(Number(match[1]), Number(match[2]) - 1, Number(match[3])));
+  };
+
+  const ageReferenceDate = () => {
+    const configured = window.appConfig?.schoolYearAgeDeadline;
+    const configuredDate = parseDateOnly(configured);
+    if (!isNaN(configuredDate.getTime())) return configuredDate;
+
+    const now = new Date();
+    const year = now.getMonth() >= 8 ? now.getFullYear() : now.getFullYear() - 1;
+    return new Date(Date.UTC(year, 8, 1));
+  };
+
   const calcAge = (d) => {
-    const dob = new Date(d);
-    const today = new Date();
-    let a = today.getFullYear() - dob.getFullYear();
-    const m = today.getMonth() - dob.getMonth();
-    if (m < 0 || (m === 0 && today.getDate() < dob.getDate())) a--;
+    const dob = parseDateOnly(d);
+    const reference = ageReferenceDate();
+    let a = reference.getUTCFullYear() - dob.getUTCFullYear();
+    const m = reference.getUTCMonth() - dob.getUTCMonth();
+    if (m < 0 || (m === 0 && reference.getUTCDate() < dob.getUTCDate())) a--;
     return a;
   };