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From: "Nick Roberts" <nickroberts@adaos.worldonline.co.uk>
Newsgroups: comp.lang.ada
Subject: Re: Ada, calendar, and daylight savings
Date: Tue, 30 Oct 2001 02:19:51 -0000
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Date: 2001-10-30T02:19:51+00:00
List-Id: <comp.lang.ada>

My suggestion is as follows:

package Ada.Calendar.Worldwide is

   type Zoned_Time is private;
   -- This type includes the offset from UTC with the actual time.

   type Time_Zone_Offset is delta 30*60.0 range -12*60*60.0 .. +12*60*60.0;
   -- An offset from UTC, in seconds, as half-hour intervals from -12 to
   -- +12 hours. Localtime = TimeUTC + offset.

   function Clock return Zoned_Time;
   -- Also concurrently ascertains the local offset from UTC.

   function Local_Time (Zoned: Zoned_Time) return Time;
   -- Returns the local time from a Zoned_Time.

   function Time_UTC (Zoned: Zoned_Time) return Time;
   -- Returns the time UTC from a Zoned_Time.

   function Difference_from_UTC (Zoned: Zoned_Time) return Time_Zone_Offset;
   -- Returns the offset from UTC for a Zoned_Time.

   function Current_Difference_from_UTC return Time_Zone_Offset;
   -- Returns the offset from UTC currently set. Could change at any time.

   function To_Zoned (Date:       Time;
                      Difference: Time_Zone_Offset := 0.0)
      return Zoned_Time;

private
   ... -- implementation defined
end Ada.Calendar.Worldwide;

I think this should go into an optional Annex.

I'd like to see the range of Day_Duration extended:

   subtype Day_Duration  is Duration range 0.0 .. 86_405.0;

in Ada.Calendar in the next revision, to allow for added leap seconds.

--
Nick Roberts


"Corey Minyard" <minyard@acm.org> wrote in message
news:3BDD94E6.2030804@acm.org...
> Marin David Condic wrote:
> ...
> I'm not saying that it needs to use UTC for implementation, but I think
> it at least needs an annex to be able to coordinate time in some way.
> And if it uses daylight savings and timezones, the program needs some
> way to get that information and do translations into different timezones.
>
> > Better that a more sophisticated time package be included as some kind
of
> > annex or optional package. That's why I suggested that it might make a
good
> > candidate for a standard component library.
>
> I'm already working on it.  I was just wondering how it should interact
> with Ada.Calendar, and I think I know now.