Remove uneccesary date_default_timezone_set calls

refs #4639

modules/monitoring/test/php/application/views/helpers/MonitoringPropertiesTest.php

@@ -82,7 +82,6 @@ class MonitoringPropertiesTest extends BaseTestCase
 
     public function testOutput2()
     {
-        date_default_timezone_set("UTC");
         $host = new HostStruct4Properties();
         $host->current_check_attempt = '5';
         $host->active_checks_enabled = '1';

test/php/library/Icinga/Web/Form/Element/DateTimePickerTest.php

@@ -11,13 +11,6 @@ use Icinga\Web\Form\Element\DateTimePicker;
 
 class DateTimeTest extends BaseTestCase
 {
-    public function setUp()
-    {
-        // Set default timezone else new DateTime calls will die with the Exception that it's
-        // not safe to rely on the system's timezone
-        date_default_timezone_set('UTC');
-    }
-
     /**
      * Test that DateTimePicker::isValid() returns false if the input is not valid in terms of being a date/time string
      * or a timestamp