Here are my rules:
public function rules()
{
return [
'start_date' => 'required|date_format:Y-m-d|after:today',
'start_time' => 'required|regex:/^\d{2}:00$/',
'start_city' => 'required|numeric',
'end_date' => 'required|date_format:Y-m-d|after:start_date',
'end_time' => 'required|regex:/^\d{2}:00$/',
'end_city' => 'required|numeric',
];
}
And the resulting documentation:

As you can see, the description for end_date is invalid. It should be something like: Must be a date after start_date