Is there a way to express 'infinite time'?

I am using the Range class to represent a range of times. Now I want a range which represents any point after a given time.

I tried (DateTime.now .. nil), but the Range class doesn't allow objects of different classes to be endpoints of the same range. (Attempting to create a Range with this property results in ArgumentError: bad value for range.)

Is there an equivalent of infinity for time, i.e. Time.now + (1.0/0.0)? Or alternately, is there a way to get around the Range class's requirement that its min and max values be of the same class?