WordPress at a glance
filter is not described

pre_get_lastpostmodified filter-hook . WP 4.4.0

Pre-filter the return value of get_lastpostmodified() before the query is run.

Usage

add_filter( 'pre_get_lastpostmodified', 'filter_function_name_879', 10, 3 );
function filter_function_name_879( $lastpostmodified, $timezone, $post_type ){
	// filter...

	return $lastpostmodified;
}
$lastpostmodified(string)
Date the last post was modified. Returning anything other than false will short-circuit the function.
$timezone(string)
Location to use for getting the post modified date. See get_lastpostdate() for accepted $timezone values.
$post_type(string)
The post type to check.

Where the hook is called

get_lastpostmodified()
pre_get_lastpostmodified
wp-includes/post.php 5909
$lastpostmodified = apply_filters( 'pre_get_lastpostmodified', false, $timezone, $post_type );

Where the hook is used (in WP core)

Does not used.