This should do it.

// See if the post is older than 24 hours.
if ( get_post_time() <= strtotime( \'-1 day\' ) ) {
  echo \'Published more than 24 hours ago.\';
} else {
  echo \'Published within the last 24 hours.\';
}

迄今为止：

function ci_posted_on() {
$time_string = \'<time itemprop="datePublished" content="%2$s" class="entry-date published updated" datetime="%1$s">%2$s</time>\';
if ( get_the_time( \'U\' ) !== get_the_modified_time( \'U\' ) ) {
    $time_string = \'<time itemprop="datePublished" content="%2$s" class="entry-date published" datetime="%1$s">%2$s</time><time itemprop="dateModified" content="%4$s" class="updated" datetime="%3$s">%4$s</time>\';
}

$time_string = sprintf( $time_string,
    esc_attr( get_the_date( \'c\' ) ),
    esc_html( get_the_date() ),
    esc_attr( get_the_modified_date( \'c\' ) ),
    esc_html( get_the_modified_date() )
);

$time_posted = esc_html( get_the_time() );
$u_time = get_the_time(\'U\'); 
$u_modified_time = get_the_modified_time(\'U\');

$posted_on = sprintf(
    _x( \'%s\', \'post date\', \'ci\' ),
    \'\' . $time_string . \'\'
);

if ($u_modified_time >= $u_time + 86400) :
   the_modified_time(\'g:i a\'); 
else :
   echo \' . $posted_on . \' at \' . $time_posted . \';