.//bekirdag

Here is a pacth for event module patch to use date popup js calendar for 5.x-1.0:

#note that you need both event and date_popup modules!

--- event.module
+++ (clipboard)
@@ -1923,6 +1923,29 @@
             '#description' => t('YYYY-MM-DD HH:MM'),
             );
         }
+        else if (module_exists('date_popup')) {
+
+          $form['start_date'] = array(
+            '#title' => t('Start Date'),
+            '#type' => 'date_popup',
+            '#default_value' => _event_date('YYYY-MM-DD HH:MM:SS', $node->event_start ? $node->event_start : _event_user_time(), $node->start_offset),
+            '#attributes' => array('class' => 'date_popup'),
+            '#size' => 19,
+            '#maxlength' => 19,
+            '#weight' => -15,
+            '#description' => t('YYYY-MM-DD HH:MM'),
+            );
+          $form['end_date'] = array(
+            '#title' => t('End Date'),
+            '#type' => 'date_popup',
+            '#default_value' => _event_date('Y-m-d H:i', $node->event_end ? $node->event_end : _event_user_time(), $node->end_offset),
+            '#attributes' => array('class' => 'date_popup'),
+            '#size' => 19,
+            '#maxlength' => 19,
+            '#weight' => -15,
+            '#description' => t('YYYY-MM-DD HH:MM'),
+            );
+        }
         else {
           $form['event_start'] = array(
             '#type' => 'fieldset',