How to eager loading with laravel on a different naming convention - laravel

Question

I have two tables. 'weeks' and 'dates'
The weeks table holds an 'startDate' and an 'endDate' Both columns a foreignKeys to the dates columns. The dates table holds an primary key id and the date.
weeks
| IDweeks | startDate | endDate |
| 1 | 2 | 6 |
dates
| IDdates | date |
| 1 | 12-03-2018 |
| 2 | 13-03-2018 |
.....
When I query the weeks, I always get the keys for startDate and endDate. I would like to get the values from the dates tables instead.
I´ve already tried to eager load the values like this:
weeks Modal
class weeks extends Model
{
//....
public function startDate()
{
return $this->belongsTo('App\date', 'startDate', 'date');
}
public function endDate()
{
return $this->belongsTo('App\date', 'endDate', 'date');
}
//....
dates Modal
class date extends Model
{
protected $primaryKey = 'IDdates';
calling the 'with()' method
public function showWeeks() {
$weeks = weeks::with('startDate')->get();
return view('weeks')->with('weeks', $weeks);
}
using in the view
#foreach ($weeks as $week )
{{ $week->startDate->date }} // produces an error like: Trying to get property 'date' of non-object
{{ $week->startDate }} // works but returns only the keys instead of the value of dates table.
#endforeach
How can I load the results of the dates table when calling the weeks?
EDIT: edited a typo in the title