[LEAPSECS] POSIX? (was Time math libraries, UTC to TAI)

[Warner Losh]

On Sat, Dec 31, 2016 at 9:31 AM, Steve Summit <scs+ls at eskimo.com> wrote:
> I'd like to say I'm not going to worry about that sort of case
> too much -- clearly, we can't implement proper leap second
> handling if we can't trust our time services to report them
> properly! -- but based on what I'm seeing on the ntp servers I'm
> sampling today, I may have been a bit too optimistic in that
> stance. :-\

Based on my actual experience debugging problems in production systems
around leap seconds, you can't trust the putative leap second
information too little. ntpd lies sometimes. GPS receivers have
firmware bugs that give the wrong results near leap seconds sometimes.
etc. To be robust, your system must cope with the lies and
prevarications as best it can. Leap seconds are the least thought
about aspect of most systems, so most people just get them wrong
through neglect, incompetence and sometimes spite. Any system that
hopes to survive in the current and foreseeable information
environment must be paranoid, ideally getting information from
multiple sources and cross checking it as best it can to try to
correct for human error (in both directions) as best it can.

Warner