Re: [LEAPSECS] 24:00 versus 00:00

From: Ed Davies <ls_at_EDAVIES.NILDRAM.CO.UK>
Date: Thu, 16 Feb 2006 21:14:32 +0000

Markus Kuhn wrote:
> With the 24-h notation, it is a very useful and well-established
> convention that 00:00 refers to midnight at the start of a date, while
> 24:00 refers to midnight at the end of a date. Thus, both "today 24:00"
> and "tomorrow 00:00" are fully equivalent representations of the same
> point in time. ....
> Writing "24:00" to terminate a time interval at exactly midnight is
> pretty common practice and is even sanctioned by ISO 8601. ....

I agree with all that is written here - the 24:00 notation
is indeed both useful and well-established and is sanctioned
by ISO 8601.

However, it raises a point which has been floating around in
the back of my head for a while. The problem is that this
notation means that we can't have second identifiers after
23:59:59 in sexagesimal - we have to break out of that system
to use 23:59:60 which seems quite ugly, at least to me.

If only the 24:00 for end of day notation wasn't in the way
we could look at positive leap seconds as just being the
result of deeming certain days to be a second longer than
most and just use 24:00:00. We wouldn't have to muck with
the lengths of any of the hours or minutes within that day.

This would scale much better when, eventually, days get longer
than 86401 seconds. Presumably before that, it'd also work
better for Martian days going to 24:39 and however many
seconds it is.

Received on Thu Feb 16 2006 - 13:15:03 PST

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