[LEAPSECS] Crunching Bulletin B numbers (POSIX time)

Warner Losh imp at bsdimp.com
Wed Feb 23 13:07:12 EST 2011

On 02/23/2011 03:53, Ian Batten wrote:

>> Having a known list of leap seconds let one recover TAI time from a cold GPS receiver in a few seconds to a minute, rather than waiting ~20 minutes for the almanac to download. Many systems have their internal clocks in TAI, but also have requirements to report time in UTC to users. Such a table would ensure these systems could come back online quickly without having to pay the 20 minute penalty. While the system may have already been down a little while when the swap is made, an extra 20 minutes can kill reliability targets for the system.

> Hang on. Let's unpick that scenario. How long would a machine have to be down such that a cached copy of the almanac no longer contained already applied leap seconds?

The computer and GPS receiver are co-packaged in one tin-can. This
tin-can is swapped out as a unit, as the operational personal lack the
skills, tools and/or training to diagnose any problems to a smaller
failure unit.


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