Use RRule->setTimezone()

Requires Icinga/ipl-scheduler#55

Author: jrauh01

library/Notifications/Widget/Timeline/Rotation.php

@@ -9,6 +9,7 @@
 use Generator;
 use Icinga\Module\Notifications\Common\Links;
 use Icinga\Module\Notifications\Forms\RotationConfigForm;
+use Icinga\Module\Notifications\Util\ScheduleTimezoneStorage;
 use ipl\I18n\Translation;
 use ipl\Scheduler\RRule;
 use ipl\Stdlib\Filter;
@@ -156,8 +157,9 @@ public function fetchTimeperiodEntries(DateTime $after, DateTime $until): Genera
                     $firstHandoff = $timeperiodEntry->start_time;
                 }
 
-                $rrule = new RRule($timeperiodEntry->rrule, $displayTimezone->getName());
-                $rrule->startAt($firstHandoff);
+                $rrule = (new RRule($timeperiodEntry->rrule))
+                    ->setTimezone(ScheduleTimezoneStorage::getScheduleTimezone())
+                    ->startAt($firstHandoff);
 
                 $length = $timeperiodEntry->start_time->diff($timeperiodEntry->end_time);
                 $limit = (((int) ceil($after->diff($until)->days / $interval)) + 1) * $limitMultiplier;