diff --git a/addtocalendar.module b/addtocalendar.module
index 3eb1998..8ae8fed 100644
--- a/addtocalendar.module
+++ b/addtocalendar.module
@@ -236,7 +236,8 @@ function addtocalendar_preprocess_field(&$variables) {
           );
 
         }
-        $build['addtocalendar']['atc_date_end']['#value'] = format_date(strtotime($build['addtocalendar']['atc_date_end']['#value']), 'custom', 'm/d/Y g:ia');
+        // Assign end date the value of start date if no date is present.
+        $build['addtocalendar']['atc_date_end']['#value'] = (!empty($build['addtocalendar']['atc_date_end']['#value'])) ? format_date(strtotime($build['addtocalendar']['atc_date_end']['#value']), 'custom', 'm/d/Y g:ia') : $date;
 
         $build['addtocalendar']['atc_timezone'] = array(
           '#type' => 'html_tag',