Ada.Calendar."+" gives peculiar result (Gnat 3.13)

[Charles Darcy <charlie@mullum.com.au>]

Hello,

	I've been using the Ada.Calendar.Time type to represent dates in my
program, and have struck a problem.

	Within a loop, I add (7 * Ada.Calendar.Day_Duration'Last) to an
Ada.Calendar.Time object, at the end of each iteration. I expected this
to advance the time by 1 week, and so it does initially. After a number
of loop iterations, however, the addition seems to advance the time by 1
week and 1 hour.

	Below is code which demonstrates the problem:


      declare
         use Ada.Text_IO;
         use Ada.Calendar;
         The_Year    : Year_Number;
         The_Month   : Month_Number;
         The_Day     : Day_Number;
         The_Seconds : Day_Duration;
         The_Date    : Time        := Time_Of (1995, 12, 2);
      begin
         for Count in 1 .. 100 loop
            Put_Line ("");
            Put_Line ("Iteration: " & Integer'Image (Count));

            Split (The_Date, The_Year, The_Month, The_Day, The_Seconds);
            Put_Line ("The_Date:");
            Put_Line ("  year:    " & Year_Number'Image (The_Year));
            Put_Line ("  month:   " & Month_Number'Image (The_Month));
            Put_Line ("  day:     " & Day_Number'Image (The_Day));
            Put_Line ("  seconds: " & Day_Duration'Image (The_Seconds));

            The_Date := The_Date + 7 * Ada.Calendar.Day_Duration'Last;
         end loop;
      end;


	The output begins with ...

Iteration:  1
The_Date:
  year:     1995
  month:    12
  day:      2
  seconds:  0.000000000

Iteration:  2
The_Date:
  year:     1995
  month:    12
  day:      9
  seconds:  0.000000000

Iteration:  3
The_Date:
  year:     1995
  month:    12
  day:      16
  seconds:  0.000000000


	... which is as I expected. However, later on ...


Iteration:  19
The_Date:
  year:     1996
  month:    4
  day:      6
  seconds:  0.000000000

Iteration:  20
The_Date:
  year:     1996
  month:    4
  day:      13
  seconds:  3600.000000000

Iteration:  21
The_Date:
  year:     1996
  month:    4
  day:      20
  seconds:  3600.000000000


	... an additional hour (the 3600 seconds) seems to have been added.
Still later, the additional hour disappears ...


Iteration:  48
The_Date:
  year:     1996
  month:    10
  day:      26
  seconds:  3600.000000000

Iteration:  49
The_Date:
  year:     1996
  month:    11
  day:      2
  seconds:  0.000000000

Iteration:  50
The_Date:
  year:     1996
  month:    11
  day:      9
  seconds:  0.000000000



	Any ideas as to what is going on ? In case its relevant, I'm using Gnat
3.13p under Linux.


regards,

Charles.


P.S.	Can anyone recommend a good Date package ?