diff --git a/source/changelog.txt b/source/changelog.txt
index d2b6674..0333ac5 100644
--- a/source/changelog.txt
+++ b/source/changelog.txt
@@ -9,6 +9,7 @@
 - Use date and time formats from general site settings 
 #### Deprecated
 #### Removed
+- Removed option "Display named offset"
 #### Fixed
 - Show group not found error message in block
 #### Security
diff --git a/source/connector-mobilizon.php b/source/connector-mobilizon.php
index 7c853e1..70e9317 100644
--- a/source/connector-mobilizon.php
+++ b/source/connector-mobilizon.php
@@ -74,11 +74,11 @@ final class Mobilizon_Connector {
 
   public function enable_activation() {
     MobilizonConnector\Settings::setDefaultOptions();
+    MobilizonConnector\Settings::removeObsoleteOptionsIfNeeded();
   }
 
   private function load_settings_globally_before_script($scriptName) {
     $settings = array(
-      'isShortOffsetNameShown' => MobilizonConnector\Settings::isShortOffsetNameShown(),
       'locale' => str_replace('_', '-', get_locale()),
       'timeZone' => wp_timezone_string(),
       'url' => MobilizonConnector\Settings::getUrl()
diff --git a/source/front/events-displayer.js b/source/front/events-displayer.js
index 62fd252..060fce3 100644
--- a/source/front/events-displayer.js
+++ b/source/front/events-displayer.js
@@ -10,7 +10,7 @@ export function displayEvents({ events, document, container, maxEventsCount }) {
   hideLoadingIndicator(container)
 
   const isShortOffsetNameShown =
-    window.MOBILIZON_CONNECTOR.isShortOffsetNameShown
+    window.MOBILIZON_CONNECTOR.isShortOffsetNameShown || false // TODO remove
   const locale = window.MOBILIZON_CONNECTOR.locale
   const timeZone = window.MOBILIZON_CONNECTOR.timeZone
 
diff --git a/source/front/formatter.js b/source/front/formatter.js
index 5deda7c..9180502 100644
--- a/source/front/formatter.js
+++ b/source/front/formatter.js
@@ -8,6 +8,7 @@ export default class Formatter {
   }
 
   static formatDate({ locale, timeZone, start, end, isShortOffsetNameShown }) {
+    // TODO also use WP general site settings
     const startDateTime = new DateTimeWrapper({
       locale,
       text: start,
diff --git a/source/includes/Constants.php b/source/includes/Constants.php
index b48e68c..d2a8e0c 100644
--- a/source/includes/Constants.php
+++ b/source/includes/Constants.php
@@ -4,3 +4,4 @@ namespace MobilizonConnector;
 const DEFAULT_EVENTS_COUNT = 5;
 const NAME = '<wordpress-name>';
 const NICE_NAME = '<wordpress-nice-name>';
+const PLUGIN_VERSION = '<wordpress-version>';
diff --git a/source/includes/Settings.php b/source/includes/Settings.php
index 6a2d1d9..f26addd 100644
--- a/source/includes/Settings.php
+++ b/source/includes/Settings.php
@@ -4,12 +4,11 @@ namespace MobilizonConnector;
 class Settings {
 
   private static $DEFAULT_OPTION_URL = 'https://mobilizon.fr';
-  private static $DEFAULT_IS_SHORT_OFFSET_NAME_SHOWN = false;
   private static $PAGE_NAME = 'wordpress_mobilizon';
   private static $OPTIONS_GROUP_NAME = 'wordpress_mobilizon';
   private static $OPTION_NAME_IS_SHORT_OFFSET_NAME_SHOWN = 'wordpress_mobilizon_is_short_offset_name_shown';
+  private static $OPTION_NAME_PLUGIN_VERSION = 'wordpress_mobilizon_plugin_version';
   private static $OPTION_NAME_URL = 'wordpress_mobilizon_url';
-  private static $SETTING_FIELD_NAME_IS_SHORT_OFFSET_NAME_SHOWN = 'wordpress_mobilizon_field_is_short_offset_name_shown';
   private static $SETTING_FIELD_NAME_URL = 'wordpress_mobilizon_field_url';
   private static $SETTINGS_SECTION_NAME = 'wordpress_mobilizon_section_general';
 
@@ -19,10 +18,6 @@ class Settings {
   }
 
   public static function init_settings() {
-    register_setting(
-      self::$OPTIONS_GROUP_NAME,
-      self::$OPTION_NAME_IS_SHORT_OFFSET_NAME_SHOWN
-    );
     register_setting(
       self::$OPTIONS_GROUP_NAME,
       self::$OPTION_NAME_URL,
@@ -46,21 +41,6 @@ class Settings {
         'label_for' => self::$SETTING_FIELD_NAME_URL
       )
     );
-    add_settings_field( // TODO remove
-      self::$SETTING_FIELD_NAME_IS_SHORT_OFFSET_NAME_SHOWN,
-      esc_html__('Display named offset', 'connector-mobilizon'),
-      'MobilizonConnector\Settings::output_field_is_short_offset_name_shown',
-      self::$PAGE_NAME,
-      self::$SETTINGS_SECTION_NAME,
-      array(
-        'label_for' => self::$SETTING_FIELD_NAME_IS_SHORT_OFFSET_NAME_SHOWN
-      )
-    );
-  }
-
-  public static function output_field_is_short_offset_name_shown($args) {
-    $isShortOffsetNameShown = self::isShortOffsetNameShown();
-    require dirname(__DIR__) . '/view/settings/is-short-offset-name-shown-field.php';
   }
 
   public static function output_field_url($args) {
@@ -101,22 +81,26 @@ class Settings {
     require dirname(__DIR__) . '/view/settings/page.php';
   }
 
-  public static function isShortOffsetNameShown() {
-    return get_option(self::$OPTION_NAME_IS_SHORT_OFFSET_NAME_SHOWN);
-  }
-
   public static function getUrl() {
     return get_option(self::$OPTION_NAME_URL);
   }
 
   public static function setDefaultOptions() {
-    add_option(self::$OPTION_NAME_IS_SHORT_OFFSET_NAME_SHOWN, self::$DEFAULT_IS_SHORT_OFFSET_NAME_SHOWN);
     add_option(self::$OPTION_NAME_URL, self::$DEFAULT_OPTION_URL);
   }
 
   public static function deleteAllOptions() {
-    delete_option(self::$OPTION_NAME_IS_SHORT_OFFSET_NAME_SHOWN);
     delete_option(self::$OPTION_NAME_URL);
   }
 
+  public static function removeObsoleteOptionsIfNeeded() {
+    $storedPluginVersion = get_option(self::$OPTION_NAME_PLUGIN_VERSION);
+    if ($storedPluginVersion !== PLUGIN_VERSION) {
+      if (version_compare($storedPluginVersion, '1.5.0', '<') ) {
+        delete_option(self::$OPTION_NAME_IS_SHORT_OFFSET_NAME_SHOWN);
+      }
+      update_option(self::$OPTION_NAME_PLUGIN_VERSION, PLUGIN_VERSION);
+    }    
+  }
+
 }
diff --git a/source/view/settings/is-short-offset-name-shown-field.php b/source/view/settings/is-short-offset-name-shown-field.php
deleted file mode 100644
index 424a011..0000000
--- a/source/view/settings/is-short-offset-name-shown-field.php
+++ /dev/null
@@ -1,15 +0,0 @@
-<?php
-namespace MobilizonConnector;
-
-// Exit if this file is called directly.
-if (!defined('ABSPATH')) {
-  exit;
-}
-?>
-<input id="<?php echo esc_attr($args['label_for']); ?>"
-  name="<?php echo esc_attr(self::$OPTION_NAME_IS_SHORT_OFFSET_NAME_SHOWN); ?>"
-  type="checkbox"
-  <?php echo $isShortOffsetNameShown == true ? 'checked' : ''; ?>>
-<p class="description">
-  <?php esc_html_e('The time zone of this WordPress installation is used. Whether the current offset should be displayed in brackets after the time, e.g. 10:00 (UTC)', 'connector-mobilizon'); ?>
-</p>