From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-0.4 required=5.0 tests=AC_FROM_MANY_DOTS,BAYES_00 autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,9fbc059a74d74032 X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2001-05-30 07:05:33 PST Path: archiver1.google.com!newsfeed.google.com!newsfeed.stanford.edu!skynet.be!isdnet!psinet-france!psiuk-f4!psiuk-p4!uknet!psiuk-n!news.pace.co.uk!nh.pace.co.uk!not-for-mail From: "Marin David Condic" Newsgroups: comp.lang.ada Subject: Re: Leap Seconds Date: Wed, 30 May 2001 10:00:36 -0400 Organization: Posted on a server owned by Pace Micro Technology plc Message-ID: <9f2ue6$hcm$1@nh.pace.co.uk> References: <9elpii$30i$1@nh.pace.co.uk> <3B0ED67B.E40A4E06@averstar.com> <9f0ciq$itb$1@nh.pace.co.uk> NNTP-Posting-Host: 136.170.200.133 X-Trace: nh.pace.co.uk 991231238 17814 136.170.200.133 (30 May 2001 14:00:38 GMT) X-Complaints-To: newsmaster@pace.co.uk NNTP-Posting-Date: 30 May 2001 14:00:38 GMT X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4522.1200 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200 Xref: archiver1.google.com comp.lang.ada:7877 Date: 2001-05-30T14:00:38+00:00 List-Id: As I said, I could easily imagine situations in which leap-seconds are going to be a big deal. You don't even need to be going to Saturn for it to be a problem. Much relative navigation depends on very accurate timekeeping and the speed of light. (186000 miles/second - it's not just a good idea, its the law! :-) For relative timekeeping, you can throw out leap seconds and be done with it. However, its a problem for absolute timekeeping. If someone outside your system is giving you a time that has leap-seconds included in it, then you need to know how many or you can't really be in synch - except in a relative sense. Just like not counting leap years, right? MDC -- Marin David Condic Senior Software Engineer Pace Micro Technology Americas www.pacemicro.com Enabling the digital revolution e-Mail: marin.condic@pacemicro.com Web: http://www.mcondic.com/ "Arthur Evans Jr" wrote in message news:ev_remove_this_ans-2905012042430001@192.168.1.254... > In article <9f0ciq$itb$1@nh.pace.co.uk>, "Marin David Condic" > I expect that an Ada program that communicates with an unmanned > (unpersoned?) space ship might care very much indeed. Suppose the > ship sends a message from somewhere near Saturn or some such, the > message including a time stamp. You can tell how far away from > earth it is by the difference between that time stamp and the time > the message is received. You might care a lot about a 1-second > error. (I assume an adequately accurate clock on the vessal.) > > Here the problem is not one Ada can solve. You would need a clock > at the receiving station that either was never corrected for leap > seconds, or you would need a table of corrections. To put it > differently, you need some sort of clock at the receiving station > that tells you how much time has elapsed since the vessal was > launched. Given that, an Ada program is easy, providing you have a > big enough field to store all those seconds. > > Art Evans