diff --git a/lib/kolab_sync_data_calendar.php b/lib/kolab_sync_data_calendar.php
--- a/lib/kolab_sync_data_calendar.php
+++ b/lib/kolab_sync_data_calendar.php
@@ -194,7 +194,7 @@
             if ($timezone && ($tz_name = $timezone->getName()) != 'UTC') {
                 $tzc = kolab_sync_timezone_converter::getInstance();
 
-                if ($tz_name = $tzc->encodeTimezone($tz_name)) {
+                if ($tz_name = $tzc->encodeTimezone($tz_name, $event['start']->format('Y-m-d'))) {
                     $result['timezone'] = $tz_name;
                 }
             }
diff --git a/lib/kolab_sync_timezone_converter.php b/lib/kolab_sync_timezone_converter.php
--- a/lib/kolab_sync_timezone_converter.php
+++ b/lib/kolab_sync_timezone_converter.php
@@ -151,18 +151,12 @@
             }
             $this->_setDefaultStartDateIfEmpty($_offsets);
 
-            $cacheId   = $this->_getCacheId('timezones', $_offsets);
-            $timezones = $this->_loadFromCache($cacheId);
-
-            if (!is_array($timezones)) {
-                $timezones = array();
-                foreach (DateTimeZone::listIdentifiers() as $timezoneIdentifier) {
-                    $timezone = new DateTimeZone($timezoneIdentifier);
-                    if (false !== ($matchingTransition = $this->_checkTimezone($timezone, $_offsets))) {
-                        $timezones[$timezoneIdentifier] = $matchingTransition['abbr'];
-                    }
+            $timezones = array();
+            foreach (DateTimeZone::listIdentifiers() as $timezoneIdentifier) {
+                $timezone = new DateTimeZone($timezoneIdentifier);
+                if (false !== ($matchingTransition = $this->_checkTimezone($timezone, $_offsets))) {
+                    $timezones[$timezoneIdentifier] = $matchingTransition['abbr'];
                 }
-                $this->_saveInCache($timezones, $cacheId);
             }
         }
 
@@ -224,36 +218,30 @@
     {
         $this->_setStartDate($_startDate);
 
-        $cacheId = $this->_getCacheId('offsets', array($_timezone));
+        $offsets = $this->_getOffsetsTemplate();
 
-        if (!($offsets = $this->_loadFromCache($cacheId))) {
-            $offsets = $this->_getOffsetsTemplate();
-
-            try {
-                $timezone = new DateTimeZone($_timezone);
-            }
-            catch (Exception $e) {
-                return null;
-            }
+        try {
+            $timezone = new DateTimeZone($_timezone);
+        }
+        catch (Exception $e) {
+            return null;
+        }
 
-            list($standardTransition, $daylightTransition) = $this->_getTransitionsForTimezoneAndYear($timezone, $this->_startDate['year']);
+        list($standardTransition, $daylightTransition) = $this->_getTransitionsForTimezoneAndYear($timezone, $this->_startDate['year']);
 
-            if ($standardTransition) {
-                $offsets['bias'] = $standardTransition['offset']/60*-1;
-                if ($daylightTransition) {
-                    $offsets = $this->_generateOffsetsForTransition($offsets, $standardTransition, 'standard', $timezone);
-                    $offsets = $this->_generateOffsetsForTransition($offsets, $daylightTransition, 'daylight', $timezone);
+        if ($standardTransition) {
+            $offsets['bias'] = $standardTransition['offset']/60*-1;
+            if ($daylightTransition) {
+                $offsets = $this->_generateOffsetsForTransition($offsets, $standardTransition, 'standard', $timezone);
+                $offsets = $this->_generateOffsetsForTransition($offsets, $daylightTransition, 'daylight', $timezone);
 
-                    //@todo how do we get the standardBias (is usually 0)?
-                    //$offsets['standardBias'] = ...
+                //@todo how do we get the standardBias (is usually 0)?
+                //$offsets['standardBias'] = ...
 
-                    $offsets['daylightBias'] = ($daylightTransition['offset'] - $standardTransition['offset'])/60*-1;
-                    $offsets['standardHour'] -= $offsets['daylightBias'] / 60;
-                    $offsets['daylightHour'] += $offsets['daylightBias'] / 60;
-                }
+                $offsets['daylightBias'] = ($daylightTransition['offset'] - $standardTransition['offset'])/60*-1;
+                $offsets['standardHour'] -= $offsets['daylightBias'] / 60;
+                $offsets['daylightHour'] += $offsets['daylightBias'] / 60;
             }
-
-            $this->_saveInCache($offsets, $cacheId);
         }
 
         return $offsets;
@@ -636,39 +624,4 @@
 
         return array($standardTransition, $daylightTransition);
     }
-
-    protected function _getCacheId($_prefix, $_offsets)
-    {
-        return $_prefix . md5(serialize($_offsets));
-    }
-
-    protected function _loadFromCache($key)
-    {
-        if ($cache = $this->getCache()) {
-            return $cache->get($key);
-        }
-
-        return false;
-    }
-
-    protected function _saveInCache($value, $key)
-    {
-        if ($cache = $this->getCache()) {
-            $cache->set($key, $value);
-        }
-    }
-
-    /**
-     * Getter for the cache engine object
-     */
-    protected function getCache()
-    {
-        if ($this->cache === null) {
-            $rcube = rcube::get_instance();
-            $cache = $rcube->get_cache_shared('activesync');
-            $this->cache = $cache ? $cache : false;
-        }
-
-        return $this->cache;
-    }
 }