Linux servers dominate the synchronized time data center market and have held a significant advantage over Microsoft Windows for clock synchronization. But recent improvements in the Windows Server base clock and networking technology have made it possible to synchronize Windows systems to within a few hundred nanoseconds of a reference source over commercial networks. Because Windows controls 90% of the desktop market as well as being important data center and cloud, high precision clock sync on Windows will significantly expand the domain where precise time can be used in applications - in finance as well as in distributed consensus and general enterprise computing. This talk will discuss general issues of desktop/server operating systems support for precise clock sync, the barriers to precise clock sync in earlier versions of Windows, the changes in newer versions, and how these were leveraged to get sub-microsecond NTP and PTP based clock sync in operation.