[LEAPSECS] Google, Amazon, now Microsoft

Brooks Harris brooks at edlmax.com
Sun May 31 15:13:58 EDT 2015

On 2015-05-31 04:40 AM, Poul-Henning Kamp wrote:
> --------
> In message<556ABECF.2050405 at edlmax.com>, Brooks Harris writes:
>> My question is, if Azure is doing this, what is Windows itself doing?
> No.
>>> for that no new information is available and the most recent
>>> guidance was that "somewhere between a second and an hour later
>>> the clock will step a second".
>> "most recent guidance" from whom?
>> As I understand it, the clock would step a second when it syncs with
>> NTP, but note there are apparently different capability NTP clients in
>> various Windows versions. But what happens in different timezones?
> Most Windows boxes don't run NTP.
I don't think that's true. As far as I know, Windows, either personal or 
Server versions, synchronize using NTP, and did so with SNTP until Win 
2000, then NTPV3, then NTPV4. I glean this from accumulated knowledge - 
its difficult to find authoritative information from Microsoft about it.

Where Servers and Windows Time Service are concerned, this is the best 
explanation I've found -

Disrupting time management in a Microsoft Windows 2008 Active Directory 
environment using NTP

There are good reference in that article.

There are more recent articles pertaining to Server versions, where 
Active Directory and the Windows Time Service (the W32Time (Windows 
Time) service) are in use.

How the Windows Time Service Works

On my personal laptop running Win 7, I don't have Active Directory, and 
the W32Time service is *not* started. But it will synchronize via the 
usual desktop "Internet Time" mechanisms. It uses either 
"time.nist.gov", "time.windows.com", etc. These are NTP servers.

> Some of them run some oddball M$ time-sync protocol where they ask
> their domain-controllers -- if they have one.
As above - the domain controller is configured or discovers an NTP 
server. The NT5DS protocol routes the NTP through the domain controller.
> Where domain-controllers get their time is anyones guess.
As above - an NTP server as configured or discovered.

Windows of any version is fundamentally following NTP.

But that doesn't answer the first question about how the Leap Second is 
applied to local time by Azure and/or Windows.

Also -

NIST Internet Time Service (ITS)

The story around Leap Seconds and Windows: It’s likely not Y2K

Part two of the story around Leap Seconds and Windows: #NotY2K



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