On 2010-12-14 07:33, Alex Shinn wrote: > I've looked into this, and I must say I concur wholeheartedly. I have > no idea what the committee was thinking when they came up with > POSIX time, but I can only assume they were under the influence of > some substance for which the idea of time passing at varying speeds > seems natural.
Wall clock time != physical time, as it is tied to Earth rotation. As long as that remains the case, we'll always have leap seconds, leap days or any other similar complications. Think of wall clock time as an arbitrary set of labels attached to physical time. > The good news is that if we have monotonic TAI time we can > easily and unambiguously convert to POSIX time when needed, > to get around any compatibility issues. No, not easily. You can't use TAI to represent dates in the future, as it would require leap seconds tables that are only published six months before the leap seconds occur. You can't use TAI to represent the current date either, as it would require current UTC-TAI difference, which most systems don't have [1]. In short, as long as UTC is the basis of civil time keeping, TAI will not solve any problems. [1] To be clear on this, NTP does not transmit current UTC-TAI difference by default. There is in fact "tai" field in ntptimeval, but it is only updated by ntpd if it has a leap seconds table, which it can obtain: 1) from a manually specified leap seconds file 2) from a trusted NTP server The fact is, only a few people run ntpd, and only a small fraction of those who do ever bother to keep and update the leap-seconds file or to setup crypto keys and designate some servers as trusted. Therefore no widely available way of tracking current UTC-TAI difference exists. _______________________________________________ Scheme-reports mailing list [email protected] http://lists.scheme-reports.org/cgi-bin/mailman/listinfo/scheme-reports
