[LEAPSECS] Crunching Bulletin B numbers (POSIX time)
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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