diff --git a/plugins/calendar/calendar.php b/plugins/calendar/calendar.php
index 16115f29..f63ce426 100644
--- a/plugins/calendar/calendar.php
+++ b/plugins/calendar/calendar.php
@@ -927,6 +927,8 @@ class calendar extends rcube_plugin
     
     if ($calendars[$calid]) {
       $calname = $calendars[$calid]['name'] ? $calendars[$calid]['name'] : $calid;
+      $calname = preg_replace('/[^a-z0-9_.-]/i', '', html_entity_decode($calname));  // to 7bit ascii
+      if (empty($calname)) $calname = $calid;
       $events = $this->driver->load_events($start, $end, null, $calid, 0);
     }
     else
diff --git a/plugins/calendar/lib/calendar_ical.php b/plugins/calendar/lib/calendar_ical.php
index 5b69a7f3..83ff1be4 100644
--- a/plugins/calendar/lib/calendar_ical.php
+++ b/plugins/calendar/lib/calendar_ical.php
@@ -427,9 +427,12 @@ class calendar_ical
       // fold lines to 75 chars
       return rcube_vcard::rfc2425_fold($ical);
   }
-  
+
   private function format_datetime($attr, $dt, $dateonly = false, $utc = false)
   {
+    if (is_numeric($dt))
+        $dt = new DateTime('@'.$dt);
+
     if ($utc)
       $dt->setTimezone(new DateTimeZone('UTC'));
 
@@ -443,7 +446,7 @@ class calendar_ical
       return $attr . $tzid . ':' . $dt->format('Ymd\THis' . ($tzid ? '' : 'Z'));
     }
   }
-  
+
   private function escpape($str)
   {
     return preg_replace('/(?<!\\\\)([\:\;\,\\n\\r])/', '\\\$1', $str);