date validation

I would like to validate date if it has to be > than $today for instance how?

$input = $request->validate(
        [
            'title' => 'required',
            'start_date' => 'required',
            'expire_date' => 'required',
            'redirect_url' => 'required',
            'status' => 'required',
            'banner' =>     'image|mimes:jpeg,png,jpg,gif,svg|max:2048|dimensions:min_width=1024',
        ], [
            'title.required' => 'Title is required',
            'start_date.required' => 'Start Date is required',
            'expire_date.required' => 'Expired Date is required',
            'redirect_url.required' => 'Redirect Url is required',
            'status.required' => 'Status is required',
            'banner.dimensions' => 'Panjang image minimal berukuran 1024 pixel'
        ]
    );

I