Issue #3513363: convertToHijri function must get a timestamp to convert the date

src/Plugin/Field/FieldFormatter/HijriDualDateFormatter.php

@@ -132,6 +132,10 @@ class HijriDualDateFormatter extends FormatterBase {
         else {
           // If it's a date string, create DateTime directly.
           $date = new \DateTime($date_value['value'], new \DateTimeZone('UTC'));
+
+          // Convert the DateTime to a timestamp.
+          $timestamp = $date->getTimestamp();
+          $date_value['value'] = $timestamp;
         }
 
         // Ensure date is valid.