[LEAPSECS] (no subject)

[Tony Finch]

On Mon, 22 Dec 2008, Peter Vince wrote:

>

> I am trying to clarify in my mind a couple of proposals, one of which is

> having no more leap-seconds in the civil (broadcast) time scale.  I'm

> sorry, I must have missed your messages where you said that a lot of

> software would fail in that scenario - could you briefly clarify please?


This isn't really about broadcast timescales, but about the semantics of
POSIX time_t. Steve proposes to provide a well-defined uniform timescale
on Unix systems by redefining time_t to follow some linear atomic
timescale instead of UTC, and that the zoneinfo/tzcode library would be
used to translate from this new version of time_t to UTC, using a leap
second table alongside the existing time zone tables.

The code to implement this has in fact already been written, 15 or more
years ago, but no-one uses it because it breaks too much stuff. For
example, there is a lot of time-handling code in the kernel, and because
it does not link with the tzcode library the proposed architecture doesn't
accommodate its requirements. There's also a lot of code which doesn't use
the C tzcode for time handling, such as the Java runtime. There is a
pervasive assumption in Unix that midnight UT is when t % 86400 == 0.

Tony.
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