Re: Leap Seconds

["Marin David Condic" <marin.condic.auntie.spam@pacemicro.com>]

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" <ev_remove_this_ans@evans.pgh.pa.us> 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