[LEAPSECS] Crunching Bulletin B numbers (POSIX time)

Warner Losh imp at bsdimp.com
Wed Feb 23 12:58:30 EST 2011

On 02/22/2011 16:19, Steve Allen wrote:

> On Tue 2011-02-22T18:01:00 -0500, Keith Winstein hath writ:

>> If you just need GPS-CC time, you're right. Adding 19 seconds gets you

>> within 1 microsecond of "TAI(USNO,MC)".

> Correct me if I'm wrong, but I think if you


> 1) buy a Meinberg NTP server

> 2) configure it to emit GPS time instead of UTC

> 3) get the zoneinfo source code files

> 4) edit the "leapseconds" file and delete all leaps before 1980

> 5) compile the zoneinfo files yourself, asking for the "right" ones

> 6) install the resulting zoneinfo files

> 7) set the system to use the "right" timezone

> 8) set the system to use your Meinberg stratum 1 NTP server


> then you have a system which is running its time_t based on GPS time,

> therefore does not have issues with leap seconds resetting the clock,

> and which produces a correct local time string for every time zone.


> The trick being that you are not POSIX-compliant and cannot exchange a

> time_t value with any POSIX-compliant system.

You could do that, but you still have the wait for UTC and the 'cold
spare' problem of a unit bing on the shelf for years and not having the
proper zoneinfo files.

The machine in question that I keep referring to is a stratum 1 GPS
receiver that also outputs a PPS for top of second of GPS time (in some
models 'more or less' thanks Motorola)...


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