https://github.com/sabre-io/Baikal/issues/1241
https://github.com/sabre-io/Baikal/issues/1325

Index: vendor/sabre/dav/lib/CalDAV/Plugin.php
--- vendor/sabre/dav/lib/CalDAV/Plugin.php.orig
+++ vendor/sabre/dav/lib/CalDAV/Plugin.php
@@ -508,14 +508,7 @@ class Plugin extends DAV\ServerPlugin
             $tzProp = '{'.self::NS_CALDAV.'}calendar-timezone';
             $tzResult = $this->server->getProperties($path, [$tzProp]);
             if (isset($tzResult[$tzProp])) {
-                // This property contains a VCALENDAR with a single
-                // VTIMEZONE.
-                $vtimezoneObj = VObject\Reader::read($tzResult[$tzProp]);
-                $calendarTimeZone = $vtimezoneObj->VTIMEZONE->getTimeZone();
-
-                // Destroy circular references so PHP will garbage collect the
-                // object.
-                $vtimezoneObj->destroy();
+                $calendarTimeZone = new DateTimeZone($tzResult[$tzProp]);
             } else {
                 // Defaulting to UTC.
                 $calendarTimeZone = new DateTimeZone('UTC');
