diff -rua date/date_timezone/date_timezone.module date-new/date_timezone/date_timezone.module
--- date/date_timezone/date_timezone.module	2008-08-14 22:00:08.000000000 -0400
+++ date-new/date_timezone/date_timezone.module	2008-08-14 22:02:25.000000000 -0400
@@ -113,14 +113,17 @@
  * When the timezone name is updated, update the offset as well.
  */
 function date_timezone_update_site($element) {
-  $timezone = $element['#value'];
-  if (empty($timezone)) {
-    form_set_value($element, $element['#offset']);
-  }
-  else {
-    variable_set('date_default_timezone_name', $timezone);
-    $date = date_make_date('now', $timezone);
-    form_set_value($element, date_offset_get($date));
+  // If the event 5.2 module is installed, the next chunk breaks things, stepping around it.
+  if (!function_exists('event_zonelist_by_name')) {
+    $timezone = $element['#value'];
+    if (empty($timezone)) {
+      form_set_value($element, $element['#offset']);
+    }
+    else {
+      variable_set('date_default_timezone_name', $timezone);
+      $date = date_make_date('now', $timezone);
+      form_set_value($element, date_offset_get($date));
+    }
   }
 }