From: "M. Warner Losh" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] FW: Bulletin C number 30 Date: Tue, 05 Jul 2005 09:44:46 -0600 (MDT) Message-ID: <[EMAIL PROTECTED]>
> : Instead of using TAI, which doesn't have leap > : seconds, you chose to use UTC, which does. > > You would be wrong there. We *DO* use TAI for our internal time > keeping. The trouble with that is two fold. One: GPS receivers tend[*] > to give you time in UTC and you need to convert the one to the other. > Second: Users want to see the UTC time on their atomic clocks, time > code counters, etc. So you're stuck displaying UTC. Both of these > are reasons for needing to know the leap seconds involved. And No, > the users aren't interested in TAI time, so displaying it instead is > not an alternative. > > Internally, all the software I've written uses time scales without > leap seconds. However, that doesn't get away from any problem except > the 't1 - t2' problem you have in utc. The main problem is that you can't directly get the UTC - TAI difference, right? If you had that, then you could always convert between them. There is however a peculiarity of which I am sure you are aware of, you would still need to know when the leap-seconds occured when doing time-differances over possible leap-second insertion points. TAI(t2) - TAI(t1) may not be equalent to UTC(t2) - UTC(t1). Video synchronisation is going UTC, but I pointed out that all sampling rates etc. is actually following TAI and not UTC. At least they chose to coordinate them when TAI = UTC which is a good start. They failed to identify the time- zone in which they where coordinated, which is another story, so their trial publication of the standard got one comment and they had to re-write those parts since they where plain wrong. Ah well. I still wonder if they finally got it all correct, since my attention was diverted away from it. Cheers, Magnus _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
