Re: Double 59; 60; or double 00?

From: M. Warner Losh <imp_at_BSDIMP.COM>
Date: Wed, 04 Jan 2006 16:29:11 -0700 (MST)

In message: <004701c61173$f7721d40$9515f204_at_computer>
            "Tom Van Baak" <tvb_at_LEAPSECOND.COM> writes:
: With the surge of leap second captures this time
: around, are there any concerns over the growing(?)
: use of double :59 second or double :00 second
: instead of :59:60 for a positive leap second?
: Although not technically correct, they do seem a
: practical, perhaps even clever, alternative -- in some
: cases -- to the upstream parsing trouble that the
: exceptional :59:60 causes.
: Given a choice I would vote for double :59 over
: double :00 since :59 is still in the previous day
: (where the leap second occurs). Also, :59 offers
: more symmetry between positive and negative
: leap seconds (58 and 00 are constant; 59 is
: double or nothing depending on leap type).

ntp implements the double 59, and that works well when one can't
represent the number as :60 (which is impossible to do in POSIX

POSIX, interestingly enough, doesn't define what happens at the
leapsecond very well. On the one hand, they officially don't exist.
On the other, if you convert 23:59:60 to a time_t using mktime, you
get 0:00:00 due to normalization that happens in mktime (a more or
less accidental effect). This leads some to conclude that the proper
POSIX sequence is with two 0's in a row. While this is a conclusion
from reading POSIX, it isn't the only conclusion.

Received on Wed Jan 04 2006 - 15:30:10 PST

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