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How the Windows Time service treats a leap second

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INTRODUCTION
This article describes how the Windows Time service treats a leap second.
More information

When the Windows Time service is working as a Network Time Protocol (NTP) client

The Windows Time service does not indicate the value of the Leap Indicator when the Windows Time service receives a packet that includes a leap second. (The Leap Indicator indicates whether an impending leap second is to be inserted or deleted in the last minute of the current day.) Therefore, after the leap second occurs, the NTP client that is running Windows Time service is one second faster than the actual time. This time difference is resolved at the next time synchronization.

For more information about Windows time synchronization, go to the following Microsoft TechNet website.

When the Windows Time service is working as an NTP server

No method exists to include a leap second explicitly for the Windows Time service when the service is working as an NTP server.

However, if an external NTP server sends a Leap Indicator that has a value of 01 to the Windows Time service NTP server, the Windows NTP server sends the same value to following NTP client. 

Note This is a "FAST PUBLISH" article created directly from within the Microsoft support organization. The information contained herein is provided as-is in response to emerging issues. As a result of the speed in making it available, the materials may include typographical errors and may be revised at any time without notice. See Terms of Use for other considerations.
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Article ID: 909614 - Last Review: 01/16/2015 06:54:00 - Revision: 8.0

Microsoft Windows Server 2003, Standard Edition (32-bit x86), Microsoft Windows Server 2003, Datacenter Edition (32-bit x86), Microsoft Windows Server 2003, Enterprise Edition (32-bit x86), Microsoft Windows XP Professional, Microsoft Windows XP Home Edition, Windows Server 2008 Standard, Windows Server 2008 Enterprise, Windows Server 2008 Datacenter, Windows Server 2008 for Itanium-Based Systems, Windows Web Server 2008, Windows Vista Home Basic, Windows Vista Home Premium, Windows Vista Enterprise, Windows Vista Business, Windows Vista Ultimate, Windows Vista Starter, Windows 7 Enterprise, Windows 7 Home Basic, Windows 7 Home Premium, Windows 7 Professional, Windows 7 Ultimate, Windows Server 2008 R2 Datacenter, Windows Server 2008 R2 Enterprise, Windows Server 2008 R2 Standard, Windows Server 2008 R2 for Itanium-Based Systems, Windows 8, Windows 8.1, Windows Server 2012 Standard, Windows Server 2012 Datacenter, Windows Server 2012 R2 Standard, Windows Server 2012 R2 Datacenter

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