an instance of class "Carbon\Carbon". code example

Example 1: carbon date from format

Carbon::createFromFormat('Y-m-d H:i:s', $request->date)->format('d-m-Y')

Example 2: add seconds to datetime carbon

Try to parse() it first:
$date = Carbon::parse($dateTime)
            ->addSeconds($seconds)
            ->format('Y-m-d H:i:s');