gnat : "ada.calendar.formatting" is not a predefined library

Hi,

When I try to compile aws, I get the following message:

mscm@[EMAIL PROTECTED]
 make build
Building libz.a (Zlib library)
gnatmake: objects up to date.
gnatmake: objects up to date.
gcc-4.2 -c -gnat05 -gnatwcfijkmruv -gnaty3abcefhiklmnoprstx -Wall -O2 
-gnatn -I- -gnatA 
/var/local/mscm/gnat/aws/AWS-gpl-2.3.0/src/aws-services-dispatchers-timer.adb
aws-services-dispatchers-timer.ads:31:06: "ADA.CALENDAR.FORMATTING" is 
not a predefined library unit
aws-services-dispatchers-timer.ads:31:06: 
"AWS.SERVICES.DISPATCHERS.TIMER (body)" depends on 
"AWS.SERVICES.DISPATCHERS.TIMER (spec)"
aws-services-dispatchers-timer.ads:31:06: 
"AWS.SERVICES.DISPATCHERS.TIMER (spec)" depends on 
"ADA.CALENDAR.FORMATTING (spec)"
gnatmake: 
"/var/local/mscm/gnat/aws/AWS-gpl-2.3.0/src/aws-services-dispatchers-timer.adb"

compilation error
make[1]: *** [build] Error 4
make: *** [src_build] Error 2

I try the following sample test:

with Ada.Calendar.Formatting;

procedure test is
begin
         Ada.Text_IO.Put_Line("test");
end test;

And get at compile time:
mscm@[EMAIL PROTECTED]
 gcc -gnat05 -c test.adb
test.adb:1:06: "ada.calendar.formatting" is not a predefined library unit

I'm under ubuntu, and it looks like something is missing in gnat, how to 
fix it?

I'm using :
mscm@[EMAIL PROTECTED]
 gnat
GNAT 4.2.1 (Ubuntu 4.2.1-5ubuntu6)
Copyright 1996-2006, Free Software Foundation, Inc.


Thanks,
Sebastien