system.timezone.yml

drupal_get_user_timezone in drupal/core/includes/bootstrap.inc

Returns the time zone of the current user.

hook_user_login in drupal/core/modules/user/user.api.php

The user just logged in.

RegionalForm::buildForm in drupal/core/modules/system/lib/Drupal/system/Form/RegionalForm.php

Implements \Drupal\Core\Form\FormInterface::buildForm().

system_form_user_register_form_alter in drupal/core/modules/system/system.module

Implements hook_form_FORM_ID_alter().

system_update_8038 in drupal/core/modules/system/system.install

Move site system regional settings from variable to config.

... See full list

default: ''
user:
  configurable: '1'
  default: '0'
  warn: '0'