diff --git a/src/applications/settings/editor/PhabricatorUserPreferencesEditor.php b/src/applications/settings/editor/PhabricatorUserPreferencesEditor.php
--- a/src/applications/settings/editor/PhabricatorUserPreferencesEditor.php
+++ b/src/applications/settings/editor/PhabricatorUserPreferencesEditor.php
@@ -19,6 +19,23 @@
     return $types;
   }
 
+  protected function expandTransaction(
+    PhabricatorLiskDAO $object,
+    PhabricatorApplicationTransaction $xaction) {
+
+    $setting_key = $xaction->getMetadataValue(
+      PhabricatorUserPreferencesTransaction::PROPERTY_SETTING);
+
+    $settings = $this->getSettings();
+    $setting = idx($settings, $setting_key);
+    if ($setting) {
+      return $setting->expandSettingTransaction($object, $xaction);
+    }
+
+    return parent::expandTransaction($object, $xaction);
+  }
+
+
   protected function getCustomTransactionOldValue(
     PhabricatorLiskDAO $object,
     PhabricatorApplicationTransaction $xaction) {
@@ -95,15 +112,7 @@
     array $xactions) {
 
     $errors = parent::validateTransaction($object, $type, $xactions);
-
-    $actor = $this->getActor();
-    $settings = PhabricatorSetting::getAllEnabledSettings($actor);
-
-    foreach ($settings as $key => $setting) {
-      $setting = clone $setting;
-      $setting->setViewer($actor);
-      $settings[$key] = $setting;
-    }
+    $settings = $this->getSettings();
 
     switch ($type) {
       case PhabricatorUserPreferencesTransaction::TYPE_SETTING:
@@ -157,4 +166,17 @@
     return $xactions;
   }
 
+  private function getSettings() {
+    $actor = $this->getActor();
+    $settings = PhabricatorSetting::getAllEnabledSettings($actor);
+
+    foreach ($settings as $key => $setting) {
+      $setting = clone $setting;
+      $setting->setViewer($actor);
+      $settings[$key] = $setting;
+    }
+
+    return $settings;
+  }
+
 }
diff --git a/src/applications/settings/setting/PhabricatorSetting.php b/src/applications/settings/setting/PhabricatorSetting.php
--- a/src/applications/settings/setting/PhabricatorSetting.php
+++ b/src/applications/settings/setting/PhabricatorSetting.php
@@ -111,4 +111,18 @@
     return $value;
   }
 
+  public function expandSettingTransaction($object, $xaction) {
+    return array($xaction);
+  }
+
+  protected function newSettingTransaction($object, $key, $value) {
+    $setting_property = PhabricatorUserPreferencesTransaction::PROPERTY_SETTING;
+    $xaction_type = PhabricatorUserPreferencesTransaction::TYPE_SETTING;
+
+    return id(clone $object->getApplicationTransactionTemplate())
+      ->setTransactionType($xaction_type)
+      ->setMetadataValue($setting_property, $key)
+      ->setNewValue($value);
+  }
+
 }
diff --git a/src/applications/settings/setting/PhabricatorTimezoneSetting.php b/src/applications/settings/setting/PhabricatorTimezoneSetting.php
--- a/src/applications/settings/setting/PhabricatorTimezoneSetting.php
+++ b/src/applications/settings/setting/PhabricatorTimezoneSetting.php
@@ -87,4 +87,16 @@
     return $option_groups;
   }
 
+  public function expandSettingTransaction($object, $xaction) {
+    // When the user changes their timezone, we also clear any ignored
+    // timezone offset.
+    return array(
+      $xaction,
+      $this->newSettingTransaction(
+        $object,
+        PhabricatorTimezoneIgnoreOffsetSetting::SETTINGKEY,
+        null),
+    );
+  }
+
 }