BackdropWebTestCase::setUp in modules/simpletest/backdrop_web_test_case.php

Sets up a Backdrop site for running functional and integration tests.

_install_configure_form in includes/install.core.inc

Form constructor for a site configuration form.

install_configure_form_submit in includes/install.core.inc

Form submission handler for install_configure_form().

system_regional_settings in modules/system/system.admin.inc

Form builder; Configure the site regional settings.

system_regional_settings_submit in modules/system/system.admin.inc

Form submission handler for regional settings.

system_update_1020 in modules/system/system.install

Convert date settings to config.