[ntp:questions] Can i control the NTP Sync?

David J Taylor david-taylor at blueyonder.neither-this-bit.nor-this-bit.co.uk
Wed Aug 13 07:44:11 UTC 2008

David Woolley wrote:
> David J Taylor wrote:
>> it to keep local time in just the same way as other systems.  If you
>> have to intervene manually you are doing something wrong.  Windows,
>> like many modern OSes, works in UTC internally.
> Using UTC internally is, I think, only true of NT, and comes from its
> VMS heritage, rather than from its Windows one.

Well, since 1992!  NT 3.1, 3.5, 4, Windows 2000, XP , Vista etc!

I'm not talking 16-bit Windows or DOS.

>  I seem to remember
> that Windows 3.x was not timezone aware, and I think that Windows 9.x
> only has per system timezone information and works internally on
>  local time. (Quite a few home users still use Windows 95 and some
> small businesses probably still do so - it might also be in embedded
> systems used by larger businesses.)

32-bit Windows such as 95/98/ME etc. all support the same time API, and 
use UTC internally.

> FAT and VFAT filesystems always use local time.  I'm not sure about

NTFS and CDFS (I think) use UTC.  Windows remains compatible when access 
the older file systes, as I hope would UNIX and its derivatives.

> Windows timezone handling is limited to a single pair of rules per
> timezone, with one (or zero) changes each way between two offsets. The 
> Olson package, used on most Linuxes and modern Unixes, can record
> all historic and all future changes, even if they are not reducible
> to one, simple, rule.
> Whilst you can force, at least some, NT systems to treat the RTC as
> UTC, most system administrators don't even know this.

It would be useful to have a record of leap seconds as well.  Is that in 
the Olson package?

For my own stuff - photos mainly - I stick with labelling in UTC time - no 
offsets at all.  My wife prefers local time in the country taken.  So her 
and my photos in Australia have names which are 11 hours (IIRC) different:


Can be fun when you are looking at photos from three different cameras 
taking multiple shots of the same subject (a group of friends on the 
Sydney Harbour bridge walk), all on (sigh) slightly different time 
settings (even though precisely synched before leaving home).


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