DirectorJobForm: allow to choose time period

application/forms/DirectorJobForm.php

@@ -48,6 +48,24 @@ class DirectorJobForm extends DirectorObjectForm
             'value' => $jobClass::getSuggestedRunInterval($this)
         ));
 
+        $periods = $this->db->enumTimeperiods();
+        if (!empty($periods)) {
+
+            $this->addElement(
+                'select',
+                'timeperiod_id',
+                array(
+                    'label' => $this->translate('Time period'),
+                    'description' => $this->translate(
+                        'The name of a time period within this job should be active.'
+                        . ' Supports only simple time periods (weekday and multiple'
+                        . ' time definitions)'
+                    ),
+                    'multiOptions' => $this->optionalEnum($periods),
+                )
+            );
+        }
+
         $this->addElement('text', 'job_name', array(
             'label'       => $this->translate('Job name'),
             'description' => $this->translate(