[NTLUG:Discuss] Slightly OT: Why would I care about Leap Seconds

[Fred James]

Chris Cox wrote:

>Leroy Tennison wrote:
>  
>
>>Fred James wrote:
>>    
>>
>>>All
>>>Why would I care about Leap Seconds?  In the first paragraph at 
>>><http://cspry.co.uk/computing/Indy_admin/TIMEZONE.html> it says: 
>>>"However, `TIMEZONE', as implemented in this way in IRIX, does not take 
>>>into account leap seconds, nor changes made by the European Union and 
>>>other bodies, in daylight savings time. The TIMEZONE settings have to be 
>>>altered manually every year, to update them, as changeovers are often 
>>>variable.**"  Do I care, and if so why?  No, I am not in the UK or 
>>>Europe - I am in Texas.  Thank you in advance for any help you may be 
>>>able to offer.
>>>Regards
>>>Fred James
>>>
>>>PS:  I am using TZ=CST6CDT5,M3.2.0/2,M11.1.0/2 to deal with the new 
>>>rules and so far testing has shown it to work on SGI IRIX 6.*, and on 
>>>Unisys UNIX SVR4 release 2.  I shall be testing on some Linux boxes soon.
>>>
>>>  
>>>      
>>>
>>Unless you are doing something esoteric and needing to keep in sync. 
>>with other machines that are "leap second aware" I would ask the 
>>question "Who cares about a second of deviation or even a minute?" Sure, 
>>with NTP you can stay within a second or two of UCT and that's not a bad 
>>idea but somewhere the "Get a life" sanity check needs to be introduced. 
>>Of course, with a question like this, "Ask five experts, get six 
>>answers" is probably going to apply.
>>    
>>
>
>Actually, using NTP you should be able to sync well within microseconds
>of time from the server (close enough for almost anything to not care).
>
>And time sync is VERY important.  There are many critical infrastructure
>services that will not operate correctly unless all hosts are in
>sync with each other.
>  
>
All
Thank you all for your replies.

I have four servers working as "time slaves" to another box acting as 
"time master", so those boxes are all in sync with each other, and I 
manually correct the master whenever it seems to be floating more than a 
minute or so off <www.time.gov> - not really much floating going on.  
The servers (out of my control) we communicate with are a mix of UNIX, 
Linux, and Windows boxes, and so far not one has complained - when I 
have checked I have found the Windows boxes to be notoriously off, and 
the UNIX boxes to be close to, but usually in disagreement with 
<www.time.gov> by a minute or two themselves, and not in agreement with 
each other or my boxes.  So I guess you could say close is good enough here.

But I am interested none the less in why I might care (as in another 
situation).  Perhaps you could expand on the the "There are many 
critical infrastructure services that will not operate correctly unless 
all hosts are in sync with each other" a little bit, please.  Thank you 
in advance for any help you may be able to offer.
Regards
Fred James