Editing Network Time Protocol (section)

=== Windows Time ===
All [[Microsoft Windows]] versions since [[Windows 2000]] include the Windows Time service (W32Time),<ref name="ciu7z">{{cite web |url=https://technet.microsoft.com/en-us/library/cc773061%28WS.10%29.aspx |title=Windows Time Service Technical Reference |publisher=technet.microsoft.com |date=2011-08-17 |access-date=2011-09-19 |archive-url=https://web.archive.org/web/20110906143547/http://technet.microsoft.com/en-us/library/cc773061(WS.10).aspx |archive-date=2011-09-06 |url-status=live}}</ref> which has the ability to synchronize the computer clock to an NTP server.

W32Time was originally implemented for the purpose of the [[Kerberos (protocol)|Kerberos]] version 5 authentication protocol, which required time to be within 5 minutes of the correct value to prevent [[replay attack]]s. The network time server in Windows 2000 Server (and Windows XP) does not implement NTP disciplined synchronization, only locally disciplined synchronization with NTP/SNTP correction.<ref name="gn3Ev">{{cite web |url=https://support.ntp.org/bin/view/Support/WindowsTimeService |title=Windows Time Service page at NTP.org |website=Support.NTP.org |date=2008-02-25 |access-date=2017-05-01 |archive-url=https://web.archive.org/web/20170514214217/http://support.ntp.org/bin/view/Support/WindowsTimeService |archive-date=2017-05-14 |url-status=live}}</ref>

Beginning with [[Windows Server 2003]] and [[Windows Vista]], the NTP provider for W32Time became compatible with a significant subset of NTPv3.<ref name="AD2ab">{{cite web |url=https://technet.microsoft.com/en-us/library/cc773013%28WS.10%29.aspx |title=How the Windows Time Service Works |publisher=technet.microsoft.com |date=2010-03-12 |access-date=2011-09-19 |archive-url=https://web.archive.org/web/20110924184432/http://technet.microsoft.com/en-us/library/cc773013(WS.10).aspx |archive-date=2011-09-24 |url-status=live}}</ref> Microsoft states that W32Time cannot reliably maintain time synchronization with one second accuracy.<ref name="kb939322">{{cite web | url = http://support.microsoft.com/kb/939322 | title = Support boundary to configure the Windows Time service for high accuracy environments | date = 2011-10-19 | publisher = [[Microsoft]] | access-date = 2008-12-10 | archive-url = https://web.archive.org/web/20090112213922/http://support.microsoft.com/kb/939322 | archive-date = 2009-01-12 | url-status = live}}</ref> If higher accuracy is desired, Microsoft recommends using a newer version of Windows or different NTP implementation.<ref name="ihlx1">{{cite web | url = https://docs.microsoft.com/en-us/archive/blogs/askds/high-accuracy-w32time-requirements | title = High Accuracy W32time Requirements | date = 2007-10-23 | author = Ned Pyle | publisher = [[Microsoft]] | access-date = 2012-08-26 | archive-url = https://web.archive.org/web/20121017165107/http://blogs.technet.com/b/askds/archive/2007/10/23/high-accuracy-w32time-requirements.aspx | archive-date = 2012-10-17 | url-status = live}}</ref>

Beginning with [[Windows 10]] version 1607 and [[Windows Server 2016]], W32Time can be configured to reach time accuracy of 1 s, 50 ms or 1&nbsp;ms under certain specified operating conditions.<ref name="FvW7f">{{cite web |url=https://technet.microsoft.com/en-us/windows-server-docs/identity/ad-ds/get-started/windows-time-service/windows-2016-accurate-time |website=technet.microsoft.com |title=Windows Server 2016 Accurate Time |access-date=2016-12-07 |archive-url=https://web.archive.org/web/20161202233231/https://technet.microsoft.com/en-us/windows-server-docs/identity/ad-ds/get-started/windows-time-service/windows-2016-accurate-time |archive-date=2016-12-02 |url-status=live}}</ref><ref name="kb939322" /><ref>{{Cite web|last=dahavey|title=Support boundary for high-accuracy time|url=https://docs.microsoft.com/en-us/windows-server/networking/windows-time-service/support-boundary|access-date=2021-07-24|website=docs.microsoft.com|language=en-us|archive-date=2 May 2021|archive-url=https://web.archive.org/web/20210502120540/https://docs.microsoft.com/en-us/windows-server/networking/windows-time-service/support-boundary|url-status=live}}</ref>