可以在“提交”元框中添加自定义下拉框：

用户只能选择未来X天。

如果日期太远，我们将发布日期设置为当前日期。

下面是我添加新帖子、更改日期并发布时的实际情况：

我们在这里看到了日程安排。

演示插件

这里有一个想法，希望您可以进一步测试并根据需要进行调整。

配置如下：

class Config
{
    const CPT       = \'post\';
    const INTERVAL  = 8;
}

其中CPT 是目标和的自定义帖子类型INTERVAL 是未来允许的最大天数。

我们使用三个类：

• Main 用于插件设置
• Dropdown 这将处理自定义下拉框
• Restrictions 保存post数据时处理限制

以下是插件：

<?php
/**
 * Plugin Name: Publish Date Restrictions
 * Plugin URI:  http://wordpress.stackexchange.com/a/205252/26350
 * Author:      Birgir Erlendsson (birgire)
 * Version:     0.0.2
 */

namespace wpse\\birgire;

add_action( \'admin_init\', function()
{
    if( class_exists( \'wpse\\birgire\\Main\' ) )
    {
        $main = new Main;
        $main->init( 
            new Dropdown, 
            new Restrictions 
        );
    }
} );

class Config
{
    const CPT       = \'post\';
    const INTERVAL  = 8;
}

interface MainInterface 
{
    public function init( DropdownInterface $dropdown, RestrictionsInterface $restrictions );
    public function wp_insert_post_data( Array $data, Array $arr );
    public function do_meta_boxes();
    public function modified_meta_box( \\WP_Post $post, Array $args );
}

interface DropdownInterface
{
    public function merge( \\WP_Post $post, $html = \'\' );
}

interface RestrictionsInterface
{
    public function post_data( Array $data, Array $arr );

}

class Dropdown implements DropdownInterface
{       
    private function get_options( \\WP_Post $post )
    {
        // current post\'s Y-m-d time
        $post_ymd = ( new \\DateTime( $post->post_date ) )->format( \'Y-m-d\' );

        // Current local timestamp
        $now = current_time( \'timestamp\' );

        // Construct custom +8days "Y-m-d" dropdown options
        $options = \'\';
        for( $i = 0; $i < (int) Config::INTERVAL; $i++ )
        {
            // Next YMD according to the local time
            $ymd = ( new \\DateTime )
                ->setTimestamp( $now )
                ->modify( sprintf( \'+%dday\', $i ) )
                ->format( \'Y-m-d\' );

            // Label
            switch ( $i ) 
            {
                case 0:
                    $label = __( \'Today\' );
                    break;
                case 1:
                    $label = __( \'Tomorrow\' );
                    break;
                default:
                    $label = $ymd;
            }

            // Options
            $options .= sprintf( 
                \'<option value="%s"%s>%s</option>\', 
                $ymd, 
                selected( $ymd, $post_ymd, 0 ),
                $label 
            );

        } // end of for loop

        return $options;
    }

    private function get_style()
    {
        // Hide the current "Y, m, d" inputs 
        // Note: We can\'t remove it with preg_replace, because of Javascript checks
        return \'
            <style>
                .timestamp-wrap label:nth-child(5),
                .timestamp-wrap label:nth-child(2),
                .timestamp-wrap label:nth-child(3),
                .timestamp-wrap label:nth-child(4) {
                    display:none !important;
                }
            </style>
        \';
    }

    private function get_html( \\WP_Post $post )
    {
        // Construct custom +8days "Y-m-d" dropdown 
        return sprintf(
            \'<label><span class="screen-reader-text">YMD</span>
                <select id="wpse_ymd" name="wpse_ymd">
                    <option value="">Select</option> %s     
                </select>
            </label>
            %s\',
            $this->get_options( $post ),
            $this->get_style()
        );  
    }   

    public function merge( \\WP_Post $post, $html = \'\' )
    {
        // Create a +8days "Y-m-d" dropdown 
        $dropdown = $this->get_html( $post );

        // Inject into the metabox HTML
        $from = \'<label><span class="screen-reader-text">Month</span>\';
        $to  = $dropdown . $from;
        return str_replace( $from, $to, $html );
    }
}


class Restrictions implements RestrictionsInterface
{
    public function post_data( Array $data, Array $arr )
    {
        // Target the corresponding post type when the restricted \'wpse_ymd\' is posted
        if(     
            ! empty( $data[\'post_type\'] ) 
            && Config::CPT !== $data[\'post_type\'] 
        )
            return $data;   

        // input date is valid
        $valid = false;

        // Current local datetime object
        $local = ( new \\DateTime )->setTimestamp( current_time( \'timestamp\' ) );

        // Process the selected custom dropdown date     
        if( ! empty( $arr[\'wpse_ymd\'] ) ) 
        {
            // Create datetime objects
            $input_date_obj = ( new \\DateTime )->createFromFormat( \'Y-m-d\', $arr[\'wpse_ymd\']   );   
            $post_date_obj  = ( new \\DateTime )->createFromFormat( \'Y-m-d H:i:s\', $data[\'post_date\'] );

            // If valid date and not too far into the future!
            if(    $this->is_valid_date( $input_date_obj )
                && (int) Config::INTERVAL  >= $this->signed_diff_in_days( $local, $input_date_obj )
            ) {
                // Create mysql date strings
                $new_post_date_obj = $post_date_obj->setDate( 
                    $input_date_obj->format( \'Y\' ), 
                    $input_date_obj->format( \'m\' ), 
                    $input_date_obj->format( \'d\' )
                );

                // Override current post_date and post_date_gmt 
                $data[\'post_date\']      = $new_post_date_obj->format( \'Y-m-d H:i:s\' );
                $data[\'post_date_gmt\']  = $new_post_date_obj->setTimezone( new \\DateTimeZone( \'GMT\' ) )->format( \'Y-m-d H:i:s\' );

                // Set status to \'future\' if > now
                if( $new_post_date_obj->format( \'timestamp\' ) > $now )
                    $data[\'post_status\'] = \'future\';

                $valid = true;
            }
        }

        // Set the post date to the current time, 
        // if user selected a date too far into the future
        if( ! $valid )
        {
            $data[\'post_date\']      = $local->format( \'Y-m-d H:i:s\' );
            $data[\'post_date_gmt\']  = $local->setTimezone( new \\DateTimeZone( \'GMT\' ) )->format( \'Y-m-d H:i:s\' );           
        }

        return $data;
    }

    private function is_valid_date( \\DateTime $obj )
    {
        return 
               is_a( $obj, \'\\DateTime\' ) 
            && 0 === $obj->getLastErrors()[\'error_count\']
            && 0 === $obj->getLastErrors()[\'warning_count\'];
    }

    private function signed_diff_in_days( \\DateTime $dt1, \\DateTime $dt2 )
    {
        $dt = $dt1->diff( $dt2 );

        // Calculate the number of days (both positive or negativve) 
        // See more here http://stackoverflow.com/a/22967760/2078474
        return $dt->days * ( $dt->invert ? -1 : 1 );        
    }

}

class Main implements MainInterface
{
    private $dropdown;
    private $restrictions;

    public function init( DropdownInterface $dropdown, RestrictionsInterface $restrictions  )
    {
        $this->restrictions  = $restrictions;
        $this->dropdown      = $dropdown;

        add_action( \'do_meta_boxes\',        [ $this, \'do_meta_boxes\' ] );       
        add_filter( \'wp_insert_post_data\',  [ $this, \'wp_insert_post_data\'], 10, 2 );
    }

    public function wp_insert_post_data( Array $data, Array $arr )
    {
        return $this->restrictions->post_data( $data, $arr );
    }

    public function do_meta_boxes()
    {
        // Remove submitdiv meta-box
        remove_meta_box( 
            \'submitdiv\', 
            sanitize_key( Config::CPT ), 
            \'side\' 
        );

        // Add it again, modified
        add_meta_box( 
            \'submitdiv\', 
            __( \'Publish\' ), 
            [ $this, \'modified_meta_box\' ], 
            sanitize_key( Config::CPT ), 
            \'side\', 
            \'high\' 
        );
    }

    public function modified_meta_box( \\WP_Post $post, Array $args )
    {
        // Inject our custom +8days "Y-m-d" dropdown
        echo $this->dropdown->merge( 
            $post,
            $this->get_meta_box( $post, $args )  // Grab the current submit box
        );      
    }

    private function get_meta_box( \\WP_Post $post, Array $args )
    {
        ob_start();
        post_submit_meta_box( $post, $args = [] );
        return ob_get_clean();      
    }


} // end class