_maybe_update_core() WordPress Function

function _maybe_update_core() {
	// Include an unmodified $wp_version.
	require ABSPATH . WPINC . '/version.php';

	$current = get_site_transient( 'update_core' );

	if ( isset( $current->last_checked, $current->version_checked )
		&& 12 * HOUR_IN_SECONDS > ( time() - $current->last_checked )
		&& $current->version_checked === $wp_version
	) {
		return;
	}

	wp_version_check();
}