>> n = DateTime.new(0) => #<DateTime: 3442115/2,0,2299161> >> n.to_s => "0000-01-01T00:00:00Z" >> n = n.new_offset(Rational(9,24)) # ←コレ => #<DateTime: 3442115/2,3/8,2299161> >> n.to_s => "0000-01-01T09:00:00+0900"</datetime:></datetime:>