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Does NTP synchronizes date format & timezone

Posted on 2014-02-11
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Last Modified: 2014-02-25
Q1:
I 'think' NTP server only syncs the timings (& if it does not differ by much),
but does it sync to the clients the TIMEZONE & date fomat?  I doubt so
but please correct me & point me to links that confirm this, if any.

Q2:
I guess when provisioning VMs, it'll just clone from the template the
timezone & date format & then we have to manually adjust as needed?
Is this valid for both Windows & Linux VMs?
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Question by:sunhux
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by:sunhux
ID: 39849949
Q3:
Does date format get slipped to another format without any human
(or script or job) intervention?  If it does, it there anything to sync date
format to ensure the entire vSphere cluster adheres to one format?
Sounds like a silly question
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by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 508 total points
ID: 39849960
Q1. Correct, TimeZone settings are shifted by the Local Device Settings. (e.g. the minutes and seconds).

Q2. Correct, when you patch, or adjust the VM, you will need to make sure TZ is correct.

Q3. Not sure I understand this question?
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by:Jaroslav Mraz
Jaroslav Mraz earned 532 total points
ID: 39850105
Q3 - NTP is standard procedure and protocol by RFC

http://www.networksorcery.com/enp/rfc/rfc958.txt

you don't need to do anything. IT is standardized client - server system so the time format is shipped by standard and the clinet is represents (SHOW) in way you have set in PC but they communicate together in standard format.

Is it understand able?
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Author Comment

by:sunhux
ID: 39850299
Q3:
I meant will there ever be possibilities that date format gets changed
by itself ie due to non-human intervention (eg: due to poor BIOS battery) ?
So far, I've seen date of a server went all the way back to earliest date the
system could support due to battery issue.

Quite a complex explanation from Jaroslav, still trying to figure it out
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by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 508 total points
ID: 39850310
The hardware clock in the PC, will ALWAYS override the NTP Request, because the NTP request is only, every, time based on sync settings.

So you could get an accurate time from NTP server, but if the hardware clock is causing issues, and not running correctly, could be out sync, before the PC syncs again!

Your PC does not SYNC every Second with the NTP server.
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by:Jaroslav Mraz
Jaroslav Mraz earned 532 total points
ID: 39850319
Oh so if i understand you this will explain


if pc is running time is ok till somehow it don't loose energy or is taken out of cable :)

after pc boots even with wrong time the NTP client software part of os will connect to preconfigured NTP server in specified interval and find that it have wrong date and time so it correct it by informations in NTP.
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sda100 earned 292 total points
ID: 39850428
There's a lot of simple explanation, here:
http://www.ntp.org/ntpfaq/NTP-s-algo.htm

ntp does not concern itself with date format, but your system's timezone setting is taken into account.

For question 1, I quote from the above page:

" For a tiny offset ntpd will adjust the local clock as usual; for small and larger offsets, ntpd will reject the reference time for a while. In the latter case the operation system's clock will continue with the last corrections effective while the new reference time is being rejected. After some time, small offsets (significantly less than a second) will be slewed (adjusted slowly), while larger offsets will cause the clock to be stepped (set anew). Huge offsets are rejected, and ntpd will terminate itself, believing something very strange must have happened."

For Linux OSes, there is normally a parameter you can specify with ntpd (the ntp time daemon) if you want ntp to adjust the time, regardless of offset, but only when the service starts (ie. reboot).  The option is "-g" and this and other options can be specified in ntp.conf.  More info on that, here:

http://www.eecis.udel.edu/~mills/ntp/html/ntpd.html

For question 2, the simple answer is "Yes".  However, if you're running VMs on ESX then I would set ESX to use ntp, and then enable the option for guests to sync time with the ESX host itself.  This is explained in more detail, here:

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1318

For question 3, ntp doesn't touch the date format.  A different date format doesn't alter what day or time it is, only that way that date/time is displayed.

Kind regards,
Steve
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Assisted Solution

by:frankhelk
frankhelk earned 268 total points
ID: 39852836
Regarding NTP, I would recommend a peek into my article about it. It would answer most of your questions.

About date format and timezone, I can definitely say that NTP not even recognizes these settings. NTP synchronizes the time by means of UTC (Universal Time Coordinated). It leaves anything related to the translation of the UTC value into localized time completely up to the OS. BTW: Any other procedure would cause significant amounts of insanity and chaos ....
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