Draft: Issue #3221245 by ckng: Option to display start date only

Closes #3221245

src/Plugin/Field/FieldFormatter/SmartDateDefaultFormatter.php

@@ -39,6 +39,7 @@ class SmartDateDefaultFormatter extends DateTimeDefaultFormatter {
       'force_chronological' => 0,
       'add_classes' => 0,
       'time_wrapper' => 1,
+      'start_date_only' => 0,
     ] + parent::defaultSettings();
   }
 
@@ -93,6 +94,14 @@ class SmartDateDefaultFormatter extends DateTimeDefaultFormatter {
       '#default_value' => $this->getSetting('time_wrapper'),
     ];
 
+    // Provide an option to display start date only.
+    $form['start_date_only'] = [
+      '#type' => 'checkbox',
+      '#title' => $this->t('Display start date only.'),
+      '#description' => $this->t('Display start date value only, i.e. hide the end date on display.'),
+      '#default_value' => $this->getSetting('start_date_only'),
+    ];
+
     return $form;
   }