invoiceninja/app/Models/ScheduledReport.php

<?php

namespace App\Models;

use Carbon;
use Illuminate\Database\Eloquent\SoftDeletes;

/**
 * Class Scheduled Report
 */
class ScheduledReport extends EntityModel
{
    use SoftDeletes;

    /**
     * @var array
     */
    protected $fillable = [
        'frequency',
        'config',
        'send_date',
    ];

    /**
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function account()
    {
        return $this->belongsTo('App\Models\Account');
    }

    /**
     * @return mixed
     */
    public function user()
    {
        return $this->belongsTo('App\Models\User')->withTrashed();
    }

    public function updateSendDate()
    {
        switch ($this->frequency) {
            case REPORT_FREQUENCY_DAILY;
                $this->send_date = Carbon::now()->addDay()->toDateString();
                break;
            case REPORT_FREQUENCY_WEEKLY:
                $this->send_date = Carbon::now()->addWeek()->toDateString();
                break;
            case REPORT_FREQUENCY_BIWEEKLY:
                $this->send_date = Carbon::now()->addWeeks(2)->toDateString();
                break;
            case REPORT_FREQUENCY_MONTHLY:
                $this->send_date = Carbon::now()->addMonth()->toDateString();
                break;
        }

        $this->save();
    }
}