WP_Widget_Calendar::update( array $new_instance, array $old_instance )

Source

File: wp-includes/widgets/class-wp-widget-calendar.php

public function update( $new_instance, $old_instance ) {
		$instance          = $old_instance;
		$instance['title'] = sanitize_text_field( $new_instance['title'] );

		return $instance;
	}