This is a column DATETIME, so there is no need for additional formatting of the instance Carbon. However, you need to use whereDateit if you want to fetch all users for which the column datecontains today's date:
$data['nowUser'] = User::whereDate('date', '=', Carbon::today())->get();
Carbon::today() Query Builder __toString DATETIME string Carbon::DEFAULT_TO_STRING_FORMAT, MySQL Y-m-d H:i:s.