Split a dateTime column into a separate date and time column in Laravel 5

I have a table called 'offers' with a column called start_date of type dateTime.

I want to split this column into two separate columns called:

• start_date of type date
• start_time of type time

To do this I have the following code:

<?php

use App\Offer;
use App\Schedule;
use Carbon\Carbon;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Database\Migrations\Migration;

class FixOffersTable extends Migration
{
    public function up()
    {
        Schema::table('offers', function(Blueprint $table)
        {
            $table->renameColumn('start_date', 'start_date_time');
            $table->renameColumn('end_date', 'end_date_time');
        });

        Schema::table('offers', function (Blueprint $table)
        {
            $table->date('start_date')->after('start_date_time')->nullable();
            $table->time('start_time')->after('start_date')->nullable();

            foreach (Offer::all() as $offer) {
                /* Cannot use model mutator, as model class can change over time, and may no longer have certain columns
                in the $casts attribute. Therefore using the raw string fetched from the MySQL database. */
                $startDateTime = Carbon::createFromFormat('Y-m-d H:i:s', $offer->getOriginal('start_date_time'));
                $offer->start_date = Carbon::createFromDate($startDateTime->year, $startDateTime->month, $startDateTime->day);
                $offer->start_time = Carbon::createFromTime($startDateTime->hour, $startDateTime->minute, $startDateTime->second);
                $offer->save();
            }
        });
    }
}

However the above gives the following error:

[Doctrine\DBAL\Schema\SchemaException]                        
There is no column with name 'start_date' on table 'offers'. 

Please help. Better methods is also welcome!

via Chebli Mohamed