On Sat, 24 Dec 2005 19:33:26 -0500
Philip Webb <[EMAIL PROTECTED]> wrote:

> There will be a leap second between 051231 235959 & 060101 000000 .
> Does anyone know how the time servers used by NTP handle this ?
> Is it just left to the local machine to realise it's  1 sec  fast
> & adjust over a few hours or does something else alert it to correct
> things ? If the former, it could create problems for those running
> experiments; if the latter, does anyone know how it is done ?
> The last leap second was 1998/9 ,

According to the RFC there has always been a mechanism, but it was not
originally automatic.  In RFC958, http://rfc.net/rfc958.html, there is
this reference

   5.4.  Leap Seconds

      A standard mechanism to effect leap-second correction is not a
      part of this specification.  It is expected that the Leap
      Indicator bits would be set by hand in the primary reference
      clocks, then trickle down to all other clocks in the network,
      which would execute the correction at the specified time and reset
      the bits.

The newer NTP standard is now RFC1305, http://rfc.net/rfc1305.html.
>From my brief look it seems that the leap seconds are listed in a
file.  The server then sets the leap indicator when needed.

> before NTP was widely used.

Not sure about that, but even the later standard is now 13 years old.
The original is 7 years older than that.  I'd be surprised if a lot of
permanently connected sites, eg Universities, haven't been using it for
a long time now.  However most home users wouldn't have had much use
for it before the growth of lower rate broadband services.

-- 
Ian.

EOM

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