[LEAPSECS] Google, Amazon, now Microsoft

Brooks Harris brooks at edlmax.com
Mon Jun 1 02:35:51 EDT 2015

Hi Tom,

On 2015-05-31 07:23 PM, Tom Van Baak wrote:
> Hi Brooks,
> I don't know enough about Windows timekeeping in general or versions of Windows in particular to give you any authoritative answer. But here's one data point that might help clarify what you and PHK are talking about.
> On Windows XP, click on the clock icon and look at the "Internet Time" tab. It says my laptop will sync against "time.nist.gov" (choice of nist or microsoft) automatically once a week (no choice). You can also manually initiate a sync.
Right. There are more choices on more recent Windows versions (Vista, 7, 
8..). And the Server versions have more choices with Windows Time 
Service turned on.
> I looked at the LAN packets during the weekly sync and it consists of a single NTP packet going out and a single reply coming back. See attached snapshot.
> So, yes, Windows uses an NTP packet. But, no, it doesn't "run NTP".
Well, it must have an NTP client application to initiate the connection 
and communicate to the NTP server, no?

This one looks to be NTPv3.

I've implemented an SNTP client on Windows and it behaves very much like 
the standard "Internet Time".

> Multiply this by 250 million [1] PC's still happily running XP and you can better understand why Microsoft hasn't been that interested in leap seconds, NTP, or participating in the hh:59:60 timestamp nightmare.
Yes, they've got a very large number of badly administrated systems in 
the field. In more tightly administrated systems it can be done better. 
But its all "good enough" for current purposes.

> It would make sense, like Google and Amazon, that their in-house data centers would want to more precisely and deterministically handle leap seconds. But note all three companies have decided to jump or smear time instead of creating a true leap second.
As I understand it its not that they are interested in "precise" or 
"accurate" time - they are interested in smoothing over the Leap Second 
to avoid problems potentially caused by the Leap Second jump in the many 
OSs running in the data centers. Its a work around for the timekeeping 
flaws and bugs in the system's computers and applications that may fail 
on Leap Seconds in one way or another.

> /tvb
> [1] https://redmondmag.com/articles/2015/04/08/windows-xp-usage.aspx
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