get_the_modified_time( string $format = '', int|WP_Post $post = null )

function get_the_modified_time( $d = '', $post = null ) {
	$post = get_post( $post );

	if ( ! $post ) {
		// For backward compatibility, failures go through the filter below.
		$the_time = false;
	} elseif ( empty( $d ) ) {
		$the_time = get_post_modified_time( get_option( 'time_format' ), false, $post, true );
	} else {
		$the_time = get_post_modified_time( $d, false, $post, true );
	}

	/**
	 * Filters the localized time a post was last modified.
	 *
	 * @since WP-2.0.0
	 * @since WP-4.6.0 Added the `$post` parameter.
	 *
	 * @param string|bool  $the_time The formatted time or false if no post is found.
	 * @param string       $d        Format to use for retrieving the time the post was
	 *                               written. Accepts 'G', 'U', or php date format. Defaults
	 *                               to value specified in 'time_format' option.
	 * @param WP_Post|null $post     WP_Post object or null if no post is found.
	 */
	return apply_filters( 'get_the_modified_time', $the_time, $d, $post );
}