Somehow I missed this comment. But as michaelcampbell wrote, in Ada you'd select the range that made sense for your application.

So if your application makes sense with 0-based (time series in your example) then you can do it:

  Cash_Flows : array (0..max_time) of Double;

It may even make sense to go negative for some things. For instance:

  Object_at_Altitude : array (-100..1000) of Object;

Or characters:

  Selected_Answers : array (range 'a'..'z') of Boolean;

Or a type that you've created:

  type Color is Red, Green, Blue, Yellow, Orange;
  Histogram_of_Colors : array (Color'Range) of Natural;

But a particularly nice thing is that arrays in Ada, unlike C, don't lose their size, so you can always do:

  for I in Cash_Flows'Range loop
    Some_Function(Cash_Flows(I));
  end loop;

So really the index never even has to be directly touched or known after creation.