WordPress at a glance
function is not described

_future_post_hook() WP 2.3.0

Hook used to schedule publication for a post marked for the future.

The $post properties used and must exist are 'ID' and 'post_date_gmt'.

This is an internal function for using it by WP core itself. It's not recommended to use this function in your code.

No Hooks.

Return

````. Null. Nothing.

Usage

_future_post_hook( $deprecated, $post );
$deprecated(int) (required)
Not used. Can be set to null. Never implemented. Not marked as deprecated with _deprecated_argument() as it conflicts with wp_transition_post_status() and the default filter for _future_post_hook().
$post(WP_Post) (required)
Post object.

Changelog

Since 2.3.0 Introduced.

Code of _future_post_hook() WP 5.7

<?php
function _future_post_hook( $deprecated, $post ) {
	wp_clear_scheduled_hook( 'publish_future_post', array( $post->ID ) );
	wp_schedule_single_event( strtotime( get_gmt_from_date( $post->post_date ) . ' GMT' ), 'publish_future_post', array( $post->ID ) );
}