RE: 00:00:00 or 24:00:00

Larry,

this all makes perfect sense to me, but what I don't get is why the %time
built-in returns 240000 if such a time doesn't even exist according to
common sense.

Bad IBM?

Peter Colpaert
Application Developer
PLI - IT - Kontich, Belgium
-----
Yoda of Borg are we. Futile is resistance, assimilated will you be.
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"Larry Ducie" <Larry_Ducie@xxxxxxxxxxx>
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28/11/2007 12:05
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Subject
RE: 00:00:00 or 24:00:00






Hi Peter,

<snip>
First of all, I'd like to know whether January 1, 2000 00:00:00 is the
same as January 1, 2000 24:00:00 (I would think that the latter actually
means January 2).

Second, which one is correct?
</snip>

There are three different answers to this question:
1) Using standards agreed for formulating the appropriate representation
of
a designated time.
In this case ISO 8601 is your guide and would suggest that they are the
same. Both are correct.

2) Common sense.
I would argue that common sense would dictate that January 1, 2000
24:00:00
should be represented as January 2, 2000 00:00:00., and the latter is
correct.

3) Number theory.
The 24-hour clock is a base-24, base-60, base-60 number system. As such
you
can never have a number 24:00:00 in it.

The time of day is calculated using the complex number system of base-24,
base-60, base-60 for HMS (ignoring decimal fractions of a second which are
base-10 down to infinitely small numbers). At 23:59:59 adding another
second
triggers the standard addition rules to apply, only the bases used differ.
Thus, the seconds column overflows and is set to 00. The full minute now
created is carried over to the minutes column. This makes the minute
column
overflow and is set to 00. The full hour now created is carried to the
hours
column. Again, we have to carry over because the hours column is now full.
Thus we set the hours column to 00 and add 1 to the DAYS column (where did
that come from???). Unless it is the 30th, or 31st, or 28th/29th of a
particular month. If it is December we have years to increment!!! :-)

So, I'd say 24:00:00 is NOT 00:00:00, and 00:00:00 is correct, but what I
say doesn't mattert. Only mathematicians, philosophers and programmers
actually care, but each for very different reasons.

Cheers

Larry Ducie