Time

[Bayley, Alistair]

> From: Simon Marlow [mailto:simonmar at microsoft.com] 
> 
> 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.


This is something I don't see any motivation for, from a user's point of
view. AFAICT, there _is_ no notion of absolute time, just time w.r.t. a
given calendar (if you view TAI and UTC as calendars). The representation of
time as "units since epoch" is "just an implementation detail" :-)

Seriously, though, what use is being able to find the difference between two
times like this? If I want the difference between two times, I want to
specify in what units the difference should be e.g. millisecs, seconds,
days, years, etc. The difference between times tA and tB might be 86400
seconds, but they might still be on the same day e.g. leap seconds, so if I
ask for (diffDays tA tB) I might get zero, one, or two, depending on the
date.

Alistair.

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