[LEAPSECS] happy anniversary pips

[Brooks Harris]

On 2014-02-12 01:46 PM, Warner Losh wrote:

> Other systems are less open, and sweep this data under the rug is also a valid conclusion.

>

>

There's no mystery how Windows handles Leap Seconds - it doesn't.
Its off by the Leap Second until it re-syncs to NTP.

How the Windows Time service treats a leap second
http://support.microsoft.com/kb/909614

Its timezone information is dynamic, held in the Registry:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones

For example -

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time 
Zones\Eastern Standard Time
Display (UTC-05:00) Eastern Time (US & Canada)
Dlt Eastern Daylight Time
MUI_Display @tzres.dll,-110
MUI_Dlt @tzres.dll,-111
MUI_Std @tzres.dll,-112
Std Eastern Standard Time
TZI BINARY

And most entries include a "Dynamic DST" key -

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time 
Zones\Eastern Standard Time\Dynamic DST
2006 BINARY
2007 BINARY
FirstEntry 2006
LastEntry 2007

These can be updated - (and probably are updated with a "Windows 
Update", I've not verified that.)

August 2013 cumulative time zone update for Windows operating systems
http://support.microsoft.com/kb/2863058

And can be individually maintained -

How to configure the daylight saving time start date and end date for 
Guatemala in Windows
http://support.microsoft.com/kb/918645

This policy of behavior makes Windows a little "safer" from Leap Seconds 
and DST changes but its time is almost certainly wrong around changes 
until it re-syncs.

-Brooks