Changing column datatype in postgreSQL with laravel 5.6 using migration

I am working with laravel 5.6 and PostgreSQL 9.6 and I am trying to change the datatype of a column date from date to integer using a migration below.

<?php

use Illuminate\Support\Facades\Schema;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class ChangeBidDateTypeInAucBiddingsTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::table('auc_biddings', function (Blueprint $table) {
            //
            $table->integer('bid_date')->change();
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::table('auc_biddings', function (Blueprint $table) {
            //
            $table->date('bid_date')->change();
        });
    }
}

But every time I run the migration I get the following error

In PDOStatement.php line 107:

SQLSTATE[42804]: Datatype mismatch: 7 ERROR: column "bid_date" cannot be cast automatically to t ype integer HINT: You might need to specify "USING bid_date::integer".

Kindly assist on how I can achieve changing a column datatype using migration. Thanks

Below are some of the codes from composer.json

"require": {
        "php": ">=7.0.0",
        "doctrine/dbal": "^2.6",
        "fideloper/proxy": "~3.3",
        "laravel/framework": "5.5.*",
        "laravel/tinker": "~1.0",
        "predis/predis": "~1.0",
        "tymon/jwt-auth": "dev-develop"
    },