diff --git a/api/manage_recurring.php b/api/manage_recurring.php
index 546c629..cfff818 100644
--- a/api/manage_recurring.php
+++ b/api/manage_recurring.php
@@ -147,18 +147,21 @@ function calculateNextRun($scheduleType, $scheduleDay, $scheduleTime) {
             break;
 
         case 'weekly':
-            $days = ['', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'];
-            $dayName = $days[$scheduleDay] ?? 'Monday';
+            $days = [1 => 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'];
+            $dayName = $days[(int)$scheduleDay] ?? 'Monday';
             $next = new DateTime("next {$dayName} " . $time);
             break;
 
         case 'monthly':
-            $day = max(1, min(28, (int)$scheduleDay));
+            $day = max(1, min(31, (int)$scheduleDay));
             $next = new DateTime();
             $next->modify('first day of next month');
-            $next->setDate($next->format('Y'), $next->format('m'), $day);
-            list($h, $m) = explode(':', $time);
-            $next->setTime((int)$h, (int)$m, 0);
+            // Clamp to last day of target month (handles Feb, 30-day months)
+            $daysInMonth = (int)$next->format('t');
+            $day = min($day, $daysInMonth);
+            $next->setDate((int)$next->format('Y'), (int)$next->format('m'), $day);
+            $parts = explode(':', $time . ':00'); // ensure at least H:M
+            $next->setTime((int)$parts[0], (int)$parts[1], 0);
             break;
 
         default:
diff --git a/models/RecurringTicketModel.php b/models/RecurringTicketModel.php
index 8d0f3f8..a066bca 100644
--- a/models/RecurringTicketModel.php
+++ b/models/RecurringTicketModel.php
@@ -176,7 +176,8 @@ class RecurringTicketModel {
                 break;
 
             case 'weekly':
-                $dayName = ['', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'][$scheduleDay] ?? 'Monday';
+                $dayNames = [1 => 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'];
+                $dayName = $dayNames[(int)$scheduleDay] ?? 'Monday';
                 $next = new DateTime("next {$dayName} " . $scheduleTime);
                 break;