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From: Adam Beneschan <adam@irvine.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada.Calendar and NTP (and Unix Epoch)
Date: Mon, 23 Jul 2012 15:07:48 -0700 (PDT)
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Date: 2012-07-23T15:07:48-07:00
List-Id: <comp.lang.ada>

On Monday, July 23, 2012 2:42:32 PM UTC-7, erlo wrote:
> The following code raises an ADA.CALENDAR.TIME_ERROR exception:
>=20
> with Calendar;
> with Calendar.Conversions;
> with Calendar.Arithmetic;
> with Calendar.Formatting;
> with Text_IO;
> with Ada.Exceptions;
>=20
> use Calendar;
> use Text_IO;
>=20
>=20
> procedure Main is
>     AdaTid : Time;
> begin
>     AdaTid :=3D Conversions.To_Ada_Time(tm_year  =3D> 00,
>                                       tm_mon   =3D> 00,
>                                       tm_day   =3D> 01,
>                                       tm_hour  =3D> 0,
>                                       tm_min   =3D> 0,
>                                       tm_sec   =3D> 0,
>                                       tm_isdst =3D> 0); -- raises excepti=
on
>=20
>=20
>     put_line(Formatting.Image(Date                  =3D> AdaTid,
>                               Include_Time_Fraction =3D> False,
>                               Time_Zone             =3D> 0));
>=20
> end Main;
>=20
> This is because Ada.Calendar starts at 1-1-1901. But NTP starts at=20
> 1-1-1900, so how can I work my way around this issue?

My gut feeling is that if NTP gives you a time in the range 1-1-1900 to 12-=
31-1900, something is pretty wrong because computers didn't exist during th=
at time period.  So I'm not really sure what the issue is.  I think you nee=
d to be more specific about what you're trying to do.  What kind of value i=
s your program using for an "NTP time"--is it an integer, and if so, what d=
oes it represent (seconds since 1-1-1900, nanoseconds since 1-1-1900, or wh=
at)?  Are you trying to see if an NTP time is less than or greater than a v=
alue of Ada.Calendar.Time, or compute the difference in seconds (or somethi=
ng else) between an NTP time value and an Ada.Calendar.Time value, or what?=
 =20

                        -- Adam