"Joseph S. Myers" wrote on 1998-06-15 09:29 UTC:
What is the `correct' time display to give for a leapsecond in a zone with an offset from UTC that is not an integral number of minutes? Have there actually been any such zones since the start of the leapsecond system?
There is no official national time zone that is defined as an offset to UTC but that does not have an integral number of minutes difference relative to UTC. Obviously, such time zones would be rather difficult to define, because there would be no obvious notation for the inserted leap second, as it could not be called 60. Paul Eggert wrote: The tm_zone member is an integer number of minutes. However, common practice (e.g. SunOS 4.x, BSD/OS, Linux) is to have a member named tm_gmtoff that is a long number of seconds. This is required for proper support of POSIX.1, which lets the user specify UTC offset to the second; it is also required for proper support of historical applications. For example, the UTC offset of Liberia was 44 minutes and 30 seconds until May 1972, and any program running on, say, Linux with the TZ environment variable set to "Africa/Monrovia" cannot operate correctly with if the UTC offset is required to be a multiple of 60 seconds. I think time zone definitions such as Liberia until May 1972 were obviously either not based on UTC or were an intellectual error of someone who tried to define it based on UTC but didn't understand UTC (which is excusable since at that time it was rather young and as we all know well, people still have understanding the concept of leap seconds today). The second offset count would only be useful to allow a good approximation of time zones that can best be described by an integral second offset relative to UT0 or UT0, but nobody interested in precision timestamps would use such a time zone today. People not interested in precision time stamps do not operate computers with clocks that have an accuracy of better than 30 seconds, so all this sounds rather academic to me anyway. Markus -- Markus G. Kuhn, Security Group, Computer Lab, Cambridge University, UK email: mkuhn at acm.org, home page: <http://www.cl.cam.ac.uk/~mgk25/>