--- modules/comment.module.orig	2006-01-21 21:22:16.000000000 +0800
+++ modules/comment.module	2006-01-21 21:45:29.275994021 +0800
@@ -1164,10 +1181,12 @@
   // Invoke other validation handlers
   comment_invoke_comment($edit, 'validate');
 
-  $check_date = strtotime($date);
-  // As of PHP 5.1.0, strtotime returns FALSE upon failure instead of -1.
-  if ($check_date === FALSE || $check_date === -1) {
-    form_set_error('date', t('You have to specify a valid date.'));
+  if (isset($edit['date'])) {
+    $check_date = strtotime($edit['date']);
+    // As of PHP 5.1.0, strtotime returns FALSE upon failure instead of -1.
+    if ($check_date === FALSE || $check_date === -1) {
+      form_set_error('date', t('You have to specify a valid date.'));
+    }
   }
   if (isset($edit['author']) && !$account = user_load(array('name' => $edit['author']))) {
     form_set_error('author', t('You have to specify a valid author.'));