Aaron Denney wnoise at ofb.net
Thu Jan 27 04:14:20 EST 2005

On 2005-01-27, Ashley Yakeley <ashley at semantic.org> wrote:
> In article 
><3429668D0E777A499EE74A7952C382D1030DE110 at EUR-MSG-01.europe.corp.microso
> ft.com>,
>  "Simon Marlow" <simonmar at microsoft.com> wrote:
>> I like the idea of having a single notion of absolute time, which is
>> independent of TAI or UTC time.  You can do arithmetic on absolute time
>> (add/subtract absolute units of time, find absolute time differences),
>> and convert to/from TAI and UTC.
>> My library happens to keep absolute time as TAI seconds since the epoch,
>> but it doesn't have to.  A representation using (days,ticks) sounds like
>> it might be hard to do arithmetic on, though.
> I think your ClockTime is a sensible way to represent absolute time for 
> TAI. But we also need something that represents (for instance) 
> "2008-08-03 11:00:00 UTC" even though we don't know what precise TAI 
> time that will be. For this I would consider using a (days,ticks) pair: 
> it allows you to do arithmetic such as "5 UTC days later" and end up 
> with the expected answer even when there are intervening leap seconds.

This seems reasonable at first glance.  What happens when the rules
for leap years change though?  (Okay, so that's really planning
ahead...)  I would in fact reify TAI for purposes of exchange with
other systems.

"Now, who wants to think about timekeeping in domains where SR and GR
effects matter?"

Aaron Denney

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