F-ckin Leap Seconds, how do they work?

Jay Ashworth jra at baylink.com
Tue Jul 3 20:26:57 UTC 2012

----- Original Message -----
> From: "Keith Medcalf" <kmedcalf at dessus.com>

> > Are you suggesting that NTP timekeeping should be based on UT1?
> The system clock should be based on UT1 and should be monotonically
> increasing since this matches the common concept of time. Calculations
> done with this value are all based on it being UT1 and using the
> "common" notion of UT1 rules. The root cause of the difficulties is
> that someone decided that the system clock would not maintain "wall
> clock" time (UT1) but rather some other timebase and then "step" that
> time to keep it in sync with UT1.

UTC is monotonic, and is based on UT1.  Just not deterministically.  :-)

The root cause *is* that someone made a bad decision about kernel 
timekeeping, but it wasn't the choice of timescale.  Non-monotonic time
is not a feature of UTC *either*.

> NTP can keep time in UTC (or anything else) if it wants, but it should
> discipline the system clock to monotonically increasing UT1.

As I undertstand it, the problem is not how NTP disciplined the kernel,
it's what the kernel does itself.

-- jra
Jay R. Ashworth                  Baylink                       jra at baylink.com
Designer                     The Things I Think                       RFC 2100
Ashworth & Associates     http://baylink.pitas.com         2000 Land Rover DII
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