Open create_poi.php and edit_poi.php in the views/pois admin panel folder. Replace lines 108-109 from:
$('#start_date_time').datetimepicker();
$('#end_date_time').datetimepicker();
to
$('#start_date_time').datetimepicker({step: 30});
$('#end_date_time').datetimepicker({step: 30});