WordPress SEO - Register current post updated year as a custom tag or variable in to the Yoast SEO plugin. We can use the %%post_updated_year%% into the title. Read more at https://maheshwaghmare.com/doc/yoast-seo-custom-template-variable/

add-current-post-updated-year.php

<?php
  if( ! function_exists( 'prefix_yoast_register_post_updated_year' ) ) :
	/**
	 * Register Current Post Publish Year
	 * 
	 * @todo Change the `prefix_` with your own custom prefix.
	 * @since 1.0.0
	 * @return void
	 */
	function prefix_yoast_register_post_updated_year() {
	    wpseo_register_var_replacement( '%%post_updated_year%%', 'prefix_get_current_post_updated_year', 'advanced', 'Post Updated Year..' );
	}
	add_action('wpseo_register_extra_replacements', 'prefix_yoast_register_post_updated_year');
endif;

if( ! function_exists( 'prefix_get_current_post_updated_year' ) ) :
	/**
	 * Return current post updated Year
	 *
	 * @todo Change the `prefix_` with your own custom prefix.
	 * @since 1.0.0
	 * @return string
	 */
	function prefix_get_current_post_updated_year() {

		if( is_singular() ) {
			$post_updated_date = get_post_field( 'post_modified', get_the_ID() );
			return date( 'Y', strtotime( $post_updated_date ) );
		}

		return date("Y");
	}
endif;