[LEAPSECS] Lets get REAL about time.

[Poul-Henning Kamp]

In message <5DB9794A-4952-4A3B-98AF-65E9573B2705 at develooper.com>, =?utf-8?Q?Ask
_Bj=C3=B8rn_Hansen?= writes:


>This is not a general date and time handling API; just a timekeeping one.


Correct, people seem to be confused about this, so let me explain:

We need an API which tells you what time *it is*, for instance for
recording and ordering transactions in a database or to *measure*
time intervals.

We also need to be able to coordinate activities between loosely
coupled computers, for instance robots in a factory, and that
mandates that we have to be able to look into the future too.

This API needs to be fast, and it needs to work without consulting
databases, files or servers.

That's what my API proposal is about.

By basing the timescale on accumulated SI seconds, you can predict
the occurence of events in the future, as long as you express the
time until they happen, in units of seconds.

But you can not express the time until future events happen in
minutes, hours, days, weeks, months or years, because all of those
have varaiable lengths, measured in seconds.

For that another API is needed, one that understands timezones, DST
and leap days and leap-seconds.  That "calendrial" API I will leave
to others to work out.

I've probably added to the confusion by specifying the linkage
between the two APIs, but since this discussion is fundamentally
about how computers deal with leap-seconds, that was a very
important aspect of the API to cover.

Apart from this confusion, I have yet to see any serious objections
to my proposal ?

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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