Hi Tom,
Thanks. I was part of that exchange. It drifted into theological debate
about operating systems. Of course the many cultures of OSs and
languages complicates the discussion, but it seems to me the timekeeping
topic needs to rise above those crusades.
I was asking questions about Windows timekeeping. I've done quite a bit
of experimentation about that. The short of it is Windows behave just
like POSIX as far as I can tell, except its epoch, represented as struct
FILETIME, is 1601-01-01T00:00:00 (UTC-like), which is, apparently the
COBOL epoch (I didn't track down the references on that). It's an
unsigned 64-bit counter with 100-nanosecond resolution. Its the
timestamp of NTFS (DOS FAT32 is different, and I didn't go there).
typedef struct _FILETIME {
DWORD dwLowDateTime;
DWORD dwHighDateTime;
} FILETIME, *PFILETIME, *LPFILETIME;
I've implemented an experimental c++ version of SNTP, including calls to
::SetSystemTime(). This behaves the same as the Windows desktop
"Internet time" updates, as far as I can tell.
Meantime, POSIX time, as implemented by the MSVC c/c++ language and
compiler, results in identical values (well, there are differences in
resolution and format) as calls to the Windows system time functions. In
fact, calls to POSIX functions like time() are wrappers to the ::system
calls, such as ::GetLocalTime().
So, conceptually, and in the context of the Leap Second discussion, or,
at least, the counting mechanisms used, there's really no difference
between Windows time and POSIX time. Of course the implementations on
various OSs and languages will differ.
-Brooks
On 2016-09-25 04:52 PM, Tom Van Baak wrote:
Brooks,
The Microsoft Azure approach of moving the leap second to local midnight has
been discussed.
I suppose you mean at LEAPSECS? If so I've missed that and be interested in the
reference.
I'd be interested in any other discussions of it as well.
There are several dozen posts in the archives starting May of 2105.
Start with this and keep clicking 'next':
https://pairlist6.pair.net/pipermail/leapsecs/2015-May/005920.html
/tvb
----- Original Message -----
From: Brooks Harris
To:leapsecs@leapsecond.com
Sent: Sunday, September 25, 2016 11:19 AM
Subject: Re: [LEAPSECS] Bloomberg announced its smear
Hi Gerry,
On 2016-09-25 07:58 AM, GERRY ASHTON wrote:
The Microsoft Azure approach of moving the leap second to local midnight has
been discussed.
I suppose you mean at LEAPSECS? If so I've missed that and be interested in the
reference. I'd be interested in any other discussions of it as well.
-Brooks
I don't know enough about Azure to say if it is acceptable in that context, but
as a general approach, I object to midnight. National authorities in the US and
Canada have decided the hour shift for daylight saving time should occur in the
very early morning, but not at midnight; though I don't know the motivations
for this choice, it's a good choice. Many deadlines occur at local midnight,
and adherence to those deadlines is more and more often decided by computer
timestamps. Thus, any time adjustments should not occur at local midnight. (Of
course, this objection applies to places where UTC midnight is local midnight.
_______________________________________________
LEAPSECS mailing list
LEAPSECS@leapsecond.com
https://pairlist6.pair.net/mailman/listinfo/leapsecs
_______________________________________________
LEAPSECS mailing list
LEAPSECS@leapsecond.com
https://pairlist6.pair.net/mailman/listinfo/leapsecs
