[ntp:hackers] Leap second list file

Hal Murray hmurray at megapathdsl.net
Sun Jan 15 23:10:00 UTC 2012

>imp at bsdimp.com said:
>> Actually, part of the protocol indicates the leap second is coming up.
>> You don't have to copy leap second files to get the notification. See
>> RFC 5905 Section 7.3 on the LI bits. It gets set during the month in
>> which the leap second is to be added or removed.

> Except that you don't know how many leap seconds have elapsed.  This makes
> running the 'right' time zone impossible. 

I missed a step.  How did we get from leap seconds to time zones?

The LI bits in the NTP packets say insert/delete a second at the end of this 
month.  That happens at midnight UTC, not local midnight.

You don't need to know how many leap seconds have already elapsed in order to 
process the next one.  All you need to know is the local time and whether to 
insert or delete a leap second, or do nothing.

I've seen proposals to distribute leap second info in the time zone files, 
but no tie in to the above quoted text.  That seems like a good idea and 
something like it is probably necessary given that POSIX pretends they don't 

These are my opinions, not necessarily my employer's.  I hate spam.

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