WordPress at a glance
function is not described

the_modified_time() WP 2.0.0

Display the time at which the post was last modified.

Hooks in function
Return

Nothing (null).

Usage

the_modified_time( $d );
$d(string)
Optional Either 'G', 'U', or php date format defaults to the value specified in the time_format option.
Default: ''

Code of the modified time: wp-includes/general-template.php VER 5.0.3

<?php
function the_modified_time($d = '') {
	/**
	 * Filters the localized time a post was last modified, for display.
	 *
	 * @since 2.0.0
	 *
	 * @param string $get_the_modified_time The formatted time.
	 * @param string $d                     The time format. Accepts 'G', 'U',
	 *                                      or php date format. Defaults to value
	 *                                      specified in 'time_format' option.
	 */
	echo apply_filters( 'the_modified_time', get_the_modified_time($d), $d );
}