[ntp:questions] Leap second functional question

Martin Burnicki martin.burnicki at meinberg.de
Tue Feb 19 11:08:37 UTC 2008


David,

David Woolley wrote:
> The date error is significant because, once one realizes there are only
> two possible days a year, it becomes unimportant when the flags are set
> and cleared.  

That is not correct. End-of-June and end-of-December are only the
_preferred_ dates. Here's a quote from paragraph "Coordinated Universal
Time (UTC)" on the USNO web page:
http://tycho.usno.navy.mil/leapsec.html

"According to the CCIR Recommendation, first preference is given to the
opportunities at the end of December and June, and second preference to
those at the end of March and September."

A similar statement can be found on the IERS web page:
http://hpiers.obspm.fr/eop-pc/earthor/utc/leapsecond.html

"According to international agreements, first preference is given to the
opportunities at the end of December and June, and second preference to
those at the end of March and September. Since the system was introduced in
1972, only dates in June and December have been used."

Up to the recent changes in ntpd (which I have not yet reviewed in detail)
ntpd would indeed have only accepted a leap second at the end of June or
December, which is obviously wrong.

Martin
-- 
Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont
Germany




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