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Applies to: Windows Server 2022, Windows Server 2019, Windows Server 2016, Windows Server 2012 R2, Windows Server 2012, Windows 10, Azure Stack HCI, versions 21H2 and 20H2
The Windows Time service (W32Time) synchronizes the date and time for all computers managed by Active Directory Domain Services (AD DS). This article covers the different tools and settings used to manage the Windows Time service.
By default, a computer that is joined to a domain synchronizes time through a domain hierarchy of time sources. However, if a computer has been manually configured to synchronize from a specific time source, perhaps because it was formerly not joined to a domain, you can reconfigure the computer to begin automatically sourcing its time from the domain hierarchy.
Most domain-joined computers have a time client type of NT5DS, which means that they synchronize time from the domain hierarchy. An exception to this is the domain controller, which functions as the primary domain controller (PDC) emulator operations master for the root forest domain. The PDC emulator operations master in turn is configured to synchronize time with an external time source.
You can achieve down to one-millisecond time accuracy in your domain. For more information, see Support boundary for high-accuracy time and see Accurate Time for Windows Server 2016.
Caution
Don't use the Net time command to configure or set a computer's clock time when the Windows Time service is running.
Also, on older computers that run Windows XP or earlier, the Net time /querysntp command displays the name of a Network Time Protocol (NTP) server with which a computer is configured to synchronize, but that NTP server is used only when the computer's time client is configured as NTP or AllSync. This command has since been deprecated.
Network port
The Windows Time service follows the Network Time Protocol (NTP) specification, which requires the use of UDP port 123 for all time synchronization. Whenever the computer synchronizes its clock or provides time to another computer, it happens over UDP port 123. This port is exclusively reserved by the Windows Time service.
Note
- If you have a computer with multiple network adapters (is multi-homed), you cannot enable the Windows Time service based on a network adapter.
- The Windows Time NTP client uses UDP port 123 for both source and destination sync requests. When using network filtering, be aware of the source port being used.
You can use the command-line tool W32tm.exe to configure Windows Time service settings and to diagnose computer time problems. W32tm.exe is the preferred command-line tool for configuring, monitoring, and troubleshooting the Windows Time service. W32tm.exe is included with Windows XP and later and Windows Server 2003 and later.
Membership in the local Administrators group is required to run W32tm.exe locally, while membership in the Domain Admins group is required to run W32tm.exe remotely.
Run W32tm.exe
- In the Windows search bar, enter cmd.
- Right-click Command Prompt, then select Run as administrator.
- At the command prompt, enter w32tm followed by the applicable parameter, as described below:
| Parameter | Description |
|---|---|
| /? | Displays the W32tm command-line help |
| /register | Registers the Windows Time service to run as a service and adds its default configuration information to the registry. |
| /unregister | Unregisters the Windows Time service and removes all of its configuration information from the registry. |
| /monitor [/domain:<domain name>] [/computers:<name>[,<name>[,<name>...]]] [/threads:<num>] | Monitors the Windows Time service. /domain: Specifies which domain to monitor. If no domain name is given, or neither the /domain nor /computers option is specified, the default domain is used. This option might be used more than once. /computers: Monitors the given list of computers. Computer names are separated by commas, with no spaces. If a name is prefixed with a *, it is treated as a PDC. This option might be used more than once. /threads: Specifies the number of computers to analyze simultaneously. The default value is 3. The allowed range is 1-50. |
| /ntte <NT time epoch> | Converts a Windows NT system time (measured in 10-7-second intervals starting from 0h 1-Jan 1601) into a readable format. |
| /ntpte <NTP time epoch> | Converts an NTP time (measured in 2-32-second intervals starting from 0h 1-Jan 1900) into a readable format. |
| /resync [/computer:<computer>] [/nowait] [/rediscover] [/soft] | Tells a computer that it should resynchronize its clock as soon as possible, throwing out all accumulated error statistics. /computer:<computer>: Specifies the computer that should resynchronize. If not specified, the local computer will resynchronize. /nowait: do not wait for resynchronization to occur; return immediately. Otherwise, wait for resynchronization to complete before returning. /rediscover: Redetects the network configuration and rediscovers network sources, then resynchronizes. /soft: Resynchronizes by using existing error statistics. This is used for compatibility purposes. |
| /stripchart /computer:<target> [/period:<refresh>] [/dataonly] [/samples:<count>] [/rdtsc] | Displays a strip chart of the offset between this computer and another computer. /computer:<target>: The computer to measure the offset against. /period:<refresh>: The time between samples, in seconds. The default is 2 seconds. /dataonly: Displays the data only, without graphics. /samples:<count>: Collects <count> samples, then stops. If not specified, samples will be collected until Ctrl+C is pressed. /rdtsc: For each sample, this option prints comma-separated values along with the headers RdtscStart, RdtscEnd, FileTime, RoundtripDelay, and NtpOffset instead of the text graphic.
|
| /config [/computer:<target>] [/update] [/manualpeerlist:<peers>] [/syncfromflags:<source>] [/LocalClockDispersion:<seconds>] [/reliable:(YES|NO)] [/largephaseoffset:<milliseconds>]** | /computer:<target>: Adjusts the configuration of <target>. If not specified, the default is the local computer. /update: Notifies the Windows Time service that the configuration has changed, causing the changes to take effect. /manualpeerlist:<peers>: Sets the manual peer list to <peers>, which is a space-delimited list of DNS or IP addresses. When specifying multiple peers, this option must be enclosed in quotes. /syncfromflags:<source>: Sets what sources the NTP client should synchronize from. <source> should be a comma-separated list of these keywords (not case sensitive):
/reliable:(YES|NO): Set whether this computer is a reliable time source. This setting is only meaningful on domain controllers.
|
| /tz | Displays the current time zone settings. |
| /dumpreg [/subkey:<key>] [/computer:<target>] | Displays the values associated with a given registry key. The default key is HKLM\System\CurrentControlSet\Services\W32Time (the root key for the Windows Time service). /subkey:<key>: Displays the values associated with subkey <key> of the default key. /computer:<target>: Queries registry settings for computer <target> |
| /query [/computer:<target>] {/source | /configuration | /peers | /status} [/verbose] | Displays the computer's Windows Time service information. This parameter was first made available for the Windows Time client in Windows Vista and Windows Server 2008. /computer:<target>: Queries the information of <target>. If not specified, the default value is the local computer. /source: Displays the time source. /configuration: Displays the configuration of run time and where the setting comes from. In verbose mode, display the undefined or unused setting too. /peers: Displays a list of peers and their status. /status: Displays Windows Time service status. /verbose: Sets the verbose mode to display more information. |
| /debug {/disable | {/enable /file:<name> /size:/<bytes> /entries:<value> [/truncate]}} | Enables or disables the local computer Windows Time service private log. This parameter was first made available for the Windows Time client in Windows Vista and Windows Server 2008. /disable: Disables the private log. /enable: Enables the private log.
|
Set client to use two time servers
To set a client computer to point to two different time servers, one named ntpserver.contoso.com and another named clock.adatum.com, type the following command at the command prompt, and then press ENTER:
w32tm /config /manualpeerlist:"ntpserver.contoso.com clock.adatum.com" /syncfromflags:manual /updateSet client to sync time automatically from a domain source
To configure a client computer that is currently synchronizing time using a manually-specified computer to synchronize time automatically from the AD domain hierarchy, run the following:
w32tm /config /syncfromflags:domhier /updatenet stop w32timenet start w32timeCheck client time configuration
To check a client configuration from a Windows-based client computer that has a host name of contosoW1, run the following command:
W32tm /query /computer:contosoW1 /configurationThe output of this command displays a list of W32time configuration parameters that are set for the client.
Important
Windows Server 2016 has improved the time synchronization algorithms to align with RFC specifications. Therefore, if you want to set the local time client to point to multiple peers, we recommended that you prepare three or more different time servers.
If you have only two time servers, you should specify the NtpserverUseAsFallbackOnly flag (0x2) to de-prioritize one of them. For example, if you want to prioritize ntpserver.contoso.com over clock.adatum.com, run the following command:
w32tm /config /manualpeerlist:"ntpserver.contoso.com,0x8 clock.adatum.com,0x2" /syncfromflags:manual /update
Additionally, you can run the following command and read the value of NtpServer in the output:
reg query HKLM\SYSTEM\CurrentControlSet\Services\W32Time\ParametersConfigure computer clock reset
In order for W32tm.exe to reset a computer clock, it first checks the offset (CurrentTimeOffset, also known as Phase Offset) between the current time and the computer clock time to determine whether the offset is less than the MaxAllowedPhaseOffset value.
CurrentTimeOffset≤MaxAllowedPhaseOffset: Adjust the computer clock gradually by using the clock rate.CurrentTimeOffset>MaxAllowedPhaseOffset: Set the computer clock immediately.
Then, to adjust the computer clock by using the clock rate, W32tm.exe calculates a PhaseCorrection value. This algorithm varies depending on the version of Windows:
Windows Server 2016 and later versions:
PhaseCorrection_raw= |CurrentTimeOffset| Ă· (16 Ă—PhaseCorrectRateĂ—pollIntervalInSeconds)MaximumCorrection= |CurrentTimeOffset| Ă· (UpdateIntervalĂ· 100)PhaseCorrection= min(PhaseCorrection_raw,MaximumCorrection)Windows Server 2012 R2 and earlier versions:
To get the SystemClockRate value, you can use the following command and convert it from seconds to clock ticks by using the formula of (seconds Ă— 1,000 Ă— 10,000):
PhaseCorrection= |CurrentTimeOffset| Ă· (PhaseCorrectRateĂ—UpdateInterval)
All versions of Windows use the same final equation to check PhaseCorrection:
PhaseCorrection≤SystemClockRate÷ 2
Note
Windows Server 2019 and Windows 10 1809 have the same formula as [Windows Server 2016 and later versions] described above by applying cumulative updates from KB5006744 onwards.
These equations use
PhaseCorrectRate,UpdateInterval,MaxAllowedPhaseOffset, andSystemClockRatemeasured in units of clock ticks. On Windows systems, 1 ms = 10,000 clock ticks.MaxAllowedPhaseOffsetis configurable in the registry. However, the registry parameter is measured in seconds instead of clock ticks.To see the
SystemClockRateandpollIntervalInSecondsvalues (measured in seconds), open a Command Prompt window and then runW32tm /query /status /verbose. This command produces output that resembles the following.
The output presents the poll interval in both clock ticks and in seconds. The equations use the value measured in seconds (the value in parentheses).
The output presents the clock rate in seconds. To see theSystemClockRatevalue in clock ticks, use the following formula:(
value in seconds) Ă— 1,000 Ă— 10,000For example, if
SystemClockRateis 0.0156250 seconds, the value that the equation uses is 156,250 clock ticks.For full descriptions of the configurable parameters and their default values, see Config entries later in this article.(Video) Win2003 Windows Time Service
The following examples show how to apply these calculations for Windows Server 2012 R2 and earlier versions.
Example: System clock rate off by four minutes
Your computer clock time is 11:05 and the actual current time is 11:09:
PhaseCorrectRate= 1
UpdateInterval= 30,000 clock ticks
SystemClockRate= 156,000 clock ticks
MaxAllowedPhaseOffset= 10 min = 600 seconds = 600 Ă— 1,000 Ă— 10,000 = 6,000,000,000 clock ticks|
CurrentTimeOffset| = 4 min = 4 Ă— 60 Ă— 1,000 Ă— 10,000 = 2,400,000,000 clock ticks
Is CurrentTimeOffset ≤ MaxAllowedPhaseOffset?
2,400,000,000 ≤ 6,000,000,000: TRUE
AND does it satisfy the following equation?
(|
CurrentTimeOffset| ÷ (PhaseCorrectRate×UpdateInterval) ≤SystemClockRate÷ 2)
Is 2,400,000,000 / (30,000 × 1) ≤ 156,000 ÷ 2
80,000 ≤ 78,000: FALSE
Therefore, W32tm.exe would set the clock back immediately.
Note
In this case, if you want to set the clock back slowly, you would also have to adjust the values of PhaseCorrectRate or UpdateInterval in the registry to make sure that the equation result is TRUE.
Example: System clock rate off by three minutes
Your computer clock time is 11:05 and the actual current time is 11:08:
PhaseCorrectRate= 1
UpdateInterval= 30,000 clock ticks
SystemClockRate= 156,000 clock ticks(Video) How to Turn a Computer into an NTP Time Server
MaxAllowedPhaseOffset= 10 min = 600 seconds = 600 Ă— 1,000 Ă— 10,000 = 6,000,000,000 clock ticks|
CurrentTimeOffset| = 3 mins = 3 Ă— 60 Ă— 1,000 Ă— 10,000 = 1,800,000,000 clock ticks
Is CurrentTimeOffset ≤ MaxAllowedPhaseOffset?
1,800,000,000 ≤ 6,000,000,000: TRUE
AND does it satisfy the following equation?
(|
CurrentTimeOffset| ÷ (PhaseCorrectRate×UpdateInterval) ≤SystemClockRate÷ 2)
(1,800,000,000) ÷ (1 × 30,000) ≤ 156,000 ÷ 2
Is 60,000 ≤ 78,000: TRUE
In this case, the clock will be set back slowly.
Using Local Group Policy Editor
The Windows Time service stores several configuration properties as registry entries. You can use Group Policy Objects (GPOs) in Local Group Policy Editor to configure most of this information. For example, you can use GPOs to configure a computer to be an NTPServer or NTPClient, configure the time synchronization mechanism, or configure a computer to be a reliable time source.
Note
Group Policy settings for the Windows Time service can be applied on Windows Server 2003, Windows Server 2003 R2, Windows Server 2008, and Windows Server 2008 R2 domain controllers and can be applied to computers running Windows Server 2003, Windows Server 2003 R2, Windows Server 2008, and Windows Server 2008 R2.
Windows stores the Windows Time service policy information in the Local Group Policy Editor under Computer Configuration\Administrative Templates\System\Windows Time Service. It stores configuration information that the policies define in the Windows registry, and then uses those registry entries to configure the registry entries specific to the Windows Time service. As a result, the values defined by Group Policy overwrite any pre-existing values in the Windows Time service section of the registry. Some of the preset GPO settings differ from the corresponding default Windows Time service registry entries.
For example, suppose you edit policy settings in the Time Providers\Configure Windows NTP Client policy. Windows loads these settings into the policy area of the registry under the following subkey:
HKLM\Software\Policies\Microsoft\W32time\TimeProviders\NtpClient
Then Windows uses the policy settings to configure the related Windows Time service registry entries under the following subkey:
HKLM\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NTPClient\
The following table lists the policies that you can configure for the Windows Time service, and the registry subkeys that those policies affect.
Note
When you remove a Group Policy setting, Windows removes the corresponding entry from the policy area of the registry.
| Group Policy1 | Registry locations2, 3 |
|---|---|
| Global Configuration Settings | W32Time W32Time\Config W32Time\Parameters |
| Time Providers\Configure Windows NTP Client | W32Time\TimeProviders\NtpClient |
| Time Providers\Enable Windows NTP Client | W32Time\TimeProviders\NtpClient |
| Time Providers\Enable Windows NTP Server | W32Time\TimeProviders\NtpServer |
1 Category path: Computer Configuration\Administrative Templates\System\Windows Time Service
2 Subkey: HKLM\SOFTWARE\Policies\Microsoft
3 Subkey: HKLM\SYSTEM\CurrentControlSet\Services
Windows registry reference
Warning
This information is provided as a reference for use in troubleshooting and validation. Windows registry keys are used by W32Time to store critical information. Don't change these values. Modifications to the registry are not validated by the registry editor or by Windows before they are applied. If the registry contains invalid values, Windows may experience unrecoverable errors.
The Windows Time service stores information in the registry at the HKLM\SYSTEM\CurrentControlSet\Services\W32Time path under the following subkeys:
- \Config
- \Parameters
- \TimeProviders\NtpClient
- \TimeProviders\NtpServer
In the following tables, "All versions" refers to Windows 7, Windows 8, Windows 10, Windows Server 2008 and Windows Server 2008 R2, Windows Server 2012 and Windows Server 2012 R2, Windows Server 2016, and Windows Server 2019.
Note
Some of the parameters in the registry are measured in clock ticks and some are measured in seconds. To convert the time from clock ticks to seconds, use these conversion factors:
- 1 minute = 60 sec
- 1 sec = 1000 ms
- 1 ms = 10,000 clock ticks on a Windows system, as described at DateTime.Ticks Property.
For example, 5 minutes becomes 5 Ă— 60 Ă— 1000 Ă— 10000 = 3,000,000,000 clock ticks.
Config entries
The Config subkey entries are located at HKLM\SYSTEM\CurrentControlSet\Services\W32Time\Config.
| Registry entry | Versions | Description |
|---|---|---|
| AnnounceFlags | All versions | Controls whether this computer is marked as a reliable time server. A computer is not marked as reliable unless it is also marked as a time server.
The default value for domain members is 10. The default value for stand-alone clients and servers is 10. |
| ChainDisable | Controls whether or not the chaining mechanism is disabled. If chaining is disabled (set to 0), a read-only domain controller (RODC) can synchronize with any domain controller, but hosts that do not have their passwords cached on the RODC will not be able to synchronize with the RODC. This is a boolean setting, and the default value is 0. | |
| ChainEntryTimeout | Specifies the maximum amount of time that an entry can remain in the chaining table before the entry is considered to be expired. Expired entries may be removed when the next request or response is processed. The default value is 16 (seconds). | |
| ChainLoggingRate | Controls the frequency at which an event that indicates the number of successful and unsuccessful chaining attempts is logged to the System log in Event Viewer. The default is 30 (minutes). | |
| ChainMaxEntries | Controls the maximum number of entries that are allowed in the chaining table. If the chaining table is full and no expired entries can be removed, any incoming requests are discarded. The default value is 128 (entries). | |
| ChainMaxHostEntries | Controls the maximum number of entries that are allowed in the chaining table for a particular host. The default value is 4 (entries). | |
| ClockAdjustmentAuditLimit | Windows Server 2016 Version 1709 and later versions; Windows 10 Version 1709 and later versions | Specifies the smallest local clock adjustments that may be logged to the W32time service event log on the target computer. The default value is 800 (parts per million - PPM). |
| ClockHoldoverPeriod | Windows Server 2016 Version 1709 and later versions; Windows 10 Version 1709 and later versions | Indicates the maximum number of seconds a system clock can nominally hold its accuracy without synchronizing with a time source. If this period of time passes without W32time obtaining new samples from any of its input providers, W32time initiates a rediscovery of time sources. Default: 7,800 seconds. |
| EventLogFlags | All versions | Controls which events that the time service logs.
|
| FrequencyCorrectRate | All versions | Controls the rate at which the clock is corrected. If this value is too small, the clock is unstable and overcorrects. If the value is too large, the clock takes a long time to synchronize. The default value on domain members is 4. The default value on stand-alone clients and servers is 4. Note |
| HoldPeriod | All versions | Controls the period of time for which spike detection is disabled in order to bring the local clock into synchronization quickly. A spike is a time sample indicating that time is off a number of seconds, and is received after good time samples have been returned consistently. The default value on domain members is 5. The default value on stand-alone clients and servers is 5. |
| LargePhaseOffset | All versions | Specifies that a time offset greater than or equal to this value in 10-7 seconds is considered a spike. A network disruption such as a large amount of traffic might cause a spike. A spike will be ignored unless it persists for a long period of time. The default value on domain members is 50000000. The default value on stand-alone clients and servers is 50000000. |
| LastClockRate | All versions | Maintained by W32Time. It contains reserved data that is used by the Windows operating system, and any changes to this setting can cause unpredictable results. The default value on domain members is 156250. The default value on stand-alone clients and servers is 156250. |
| LocalClockDispersion | All versions | Controls the dispersion (in seconds) that you must assume when the only time source is the built-in CMOS clock. The default value on domain members is 10. The default value on stand-alone clients and servers is 10. |
| MaxAllowedPhaseOffset | All versions | Specifies the maximum offset (in seconds) for which W32Time attempts to adjust the computer clock by using the clock rate. When the offset exceeds this rate, W32Time sets the computer clock directly. The default value for domain members is 300. The default value for stand-alone clients and servers is 1. |
| MaxClockRate | All versions | Maintained by W32Time. It contains reserved data that is used by the Windows operating system, and any changes to this setting can cause unpredictable results. The default value for domain members is 155860. The default value for stand-alone clients and servers is 155860. |
| MaxNegPhaseCorrection | All versions | Specifies the largest negative time correction, in seconds, that the service makes. If the service determines that a change larger than this is required, it logs an event instead. Note The default value for domain members is 0xFFFFFFFF (hexadecimal). The default value for domain controllers is 172,800 (48 hrs). The default value for stand-alone clients and servers is 54,000 (15 hrs). |
| MaxPollInterval | All versions | Specifies the largest interval, in log2 seconds, allowed for the system polling interval. A system must poll according to the scheduled interval, a provider can refuse to produce samples when requested to do so. The default value for domain controllers is 10. The default value for domain members is 15. The default value for stand-alone clients and servers is 15. |
| MaxPosPhaseCorrection | All versions | Specifies the largest positive time correction in seconds that the service makes. If the service determines that a change larger than this is required, it logs an event instead. Note The default value for domain members is 0xFFFFFFFF (hexadecimal). The default value for domain controllers is 172,800 (48 hrs). The default value for stand-alone clients and servers is 54,000 (15 hrs). |
| MinClockRate | All versions | Maintained by W32Time. It contains reserved data that is used by the Windows operating system, and any changes to this setting can cause unpredictable results. The default value for domain members is 155860. The default value for stand-alone clients and servers is 155860. |
| MinPollInterval | All versions | Specifies the smallest interval, in log base 2 seconds, allowed for the system polling interval. A system does not request samples more frequently than this, a provider can produce samples at times other than the scheduled interval. The default value for domain controllers is 6. The default value for domain members is 10. The default value for stand-alone clients and servers is 10. |
| PhaseCorrectRate | All versions | Controls the rate at which the phase error is corrected. Specifying a small value corrects the phase error quickly, but might cause the clock to become unstable. If the value is too large, it takes a longer time to correct the phase error. The default value on domain members is 1. The default value on stand-alone clients and servers is 7. Note |
| PollAdjustFactor | All versions | Controls the decision to increase or decrease the poll interval for the system. The larger the value, the smaller the amount of error that causes the poll interval to be decreased. The default value on domain members is 5. The default value on stand-alone clients and servers is 5. |
| RequireSecureTimeSyncRequests | Windows 8 and later versions | Controls whether or not the DC will respond to time sync requests that use older authentication protocols. If enabled (set to 1), the DC will not respond to requests using such protocols. This is a boolean setting, and the default value is 0. |
| SpikeWatchPeriod | All versions | Specifies the amount of time that a suspicious offset must persist before it is accepted as correct (in seconds). The default value on domain members is 900. The default value on stand-alone clients and workstations is 900. |
| TimeJumpAuditOffset | All versions | An unsigned integer that indicates the time jump audit threshold, in seconds. If the time service adjusts the local clock by setting the clock directly, and the time correction is more than this value, then the time service logs an audit event. |
| UpdateInterval | All versions | Specifies the number of clock ticks between phase correction adjustments. The default value for domain controllers is 100. The default value for domain members is 30,000. The default value for stand-alone clients and servers is 360,000. Note |
| UtilizeSslTimeData | Windows versions later than Windows 10 build 1511 | Value of 1 indicates that W32Time uses multiple SSL timestamps to seed a clock that is grossly inaccurate. |
Parameters entries
The Parameters subkey entries are located at HKLM\SYSTEM\CurrentControlSet\Services\W32Time\Parameters.
| Registry entry | Versions | Description |
|---|---|---|
| AllowNonstandardModeCombinations | All versions | Indicates that non-standard mode combinations are allowed in synchronization between peers. The default value for domain members is 1. The default value for stand-alone clients and servers is 1. |
| NtpServer | All versions | Specifies a space-delimited list of peers from which a computer obtains time stamps, consisting of one or more DNS names or IP addresses per line. Each DNS name or IP address listed must be unique. Computers connected to a domain must synchronize with a more reliable time source, such as the official U.S. time clock.
There is no default value for this registry entry on domain members. The default value on stand-alone clients and servers is time.windows.com,0x1. |
| ServiceDll | All versions | Maintained by W32Time. It contains reserved data that is used by the Windows operating system, and any changes to this setting can cause unpredictable results. The default location for this DLL on both domain members and stand-alone clients and servers is %windir%\System32\W32Time.dll. |
| ServiceMain | All versions | Maintained by W32Time. It contains reserved data that is used by the Windows operating system, and any changes to this setting can cause unpredictable results. The default value on domain members is SvchostEntry_W32Time. The default value on stand-alone clients and servers is SvchostEntry_W32Time. |
| Type | All versions | Indicates which peers to accept synchronization from:
|
NtpClient entries
The NtpClient subkey entries are located at HKLM\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpClient
| Registry entry | Version | Description |
|---|---|---|
| AllowNonstandardModeCombinations | All versions | Indicates that non-standard mode combinations are allowed in synchronization between peers. The default value for domain members is 1. The default value for stand-alone clients and servers is 1. |
| CompatibilityFlags | All versions | Specifies the following compatibility flags and values:
|
| CrossSiteSyncFlags | All versions | Determines whether the service chooses synchronization partners outside the domain of the computer. The options and values are:
|
| DllName | All versions | Specifies the location of the DLL for the time provider. The default location for this DLL on both domain members and stand-alone clients and servers is %windir%\System32\W32Time.dll. |
| Enabled | All versions | Indicates if the NtpClient provider is enabled in the current Time Service.
|
| EventLogFlags | All versions | Specifies the events logged by the Windows Time service.
|
| InputProvider | All versions | Indicates whether to enable the NtpClient as an InputProvider, which obtains time information from the NtpServer. The NtpServer is a time server that responds to client time requests on the network by returning time samples that are useful for synchronizing the local clock.
|
| LargeSampleSkew | All versions | Specifies the large sample skew for logging, in seconds. To comply with Security and Exchange Commission (SEC) specifications, this should be set to three seconds. Events will be logged for this setting only when EventLogFlags is explicitly configured for 0x2 large sample skew. The default value on domain members is 3. The default value on stand-alone clients and servers is 3. |
| ResolvePeerBackOffMaxTimes | All versions | Specifies the maximum number of times to double the wait interval when repeated attempts to locate a peer to synchronize with fail. A value of zero means that the wait interval is always the minimum. The default value on domain members is 7. The default value on stand-alone clients and servers is 7. |
| ResolvePeerBackoffMinutes | All versions | Specifies the initial interval to wait, in minutes, before attempting to locate a peer to synchronize with. The default value on domain members is 15. The default value on stand-alone clients and servers is 15. |
| SpecialPollInterval | All versions | Specifies the special poll interval, in seconds, for manual peers. When the SpecialInterval 0x1 flag is enabled, W32Time uses this poll interval instead of a poll interval determined by the operating system. The default value on domain members is 3,600. The default value on stand-alone clients and servers is 604,800. New for build 1703, SpecialPollInterval is contained by the MinPollInterval and MaxPollInterval Config registry values. |
| SpecialPollTimeRemaining | All versions | Maintained by W32Time. It contains reserved data that is used by the Windows operating system. It specifies the time, in seconds, before W32Time will resynchronize after the computer has restarted. Any changes to this setting can cause unpredictable results. The default value on both domain members and on stand-alone clients and servers is left blank. |
NtpServer entries
The NtpServer subkey entries are located at HKLM\SYSTEM\CurrentControlSet\Services\W32Time\TimeProviders\NtpServer.
| Registry Entry | Versions | Description |
|---|---|---|
| AllowNonstandardModeCombinations | All versions | Indicates that non-standard mode combinations are allowed in synchronization between clients and servers. The default value for domain members is 1. The default value for stand-alone clients and servers is 1. |
| DllName | All versions | Specifies the location of the DLL for the time provider. The default location for this DLL on both domain members and stand-alone clients and servers is %windir%\System32\W32Time.dll. |
| Enabled | All versions | Indicates if the NtpServer provider is enabled in the current Time Service.
|
| InputProvider | All versions | Indicates whether to enable the NtpClient as an InputProvider, which obtains time information from the NtpServer. The NtpServer is a time server that responds to client time requests on the network by returning time samples that are useful for synchronizing the local clock.
|
Enhanced logging
The following registry entries are not a part of the W32Time default configuration but can be added to the registry to obtain enhanced logging capabilities. The information logged to the System Event log can be modified by changing values for the EventLogFlags setting in the Group Policy Object Editor. By default, the Windows Time service logs an event every time that it switches to a new time source.
In order to enable W32Time logging, add the following registry entries:
| Entry | Versions | Description |
|---|---|---|
| FileLogEntries | All versions | Controls the number of entries created in the Windows Time log file. The default value is none, which does not log any Windows Time activity. Valid values are 0 to 300. This value does not affect the event log entries normally created by Windows Time |
| FileLogName | All versions | Controls the location and file name of the Windows Time log. The default value is blank, and should not be changed unless FileLogEntries is changed. A valid value is a full path and file name that Windows Time will use to create the log file. This value does not affect the event log entries normally created by Windows Time. |
| FileLogSize | All versions | Controls the circular logging behavior of Windows Time log files. When FileLogEntries and FileLogName are defined, defines the size, in bytes, to allow the log file to reach before overwriting the oldest log entries with new entries. Please use 1000000 or larger value for this setting. This value does not affect the event log entries normally created by Windows Time. |
Group Policy Object settings
Group Policy settings are contained in the Global Configuration Settings and the Windows NTP Client Settings GPOs.
Global Configuration Settings
These are the global Group Policy settings and default values for the Windows Time service. These settings are contained in the Global Configuration Settings GPO in Local Policy Editor.
| Group Policy setting | Default value |
|---|---|
| AnnounceFlags | 10 |
| EventLogFlags | 2 |
| FrequencyCorrectRate | 4 |
| HoldPeriod | 5 |
| LargePhaseOffset | 1,280,000 |
| LocalClockDispersion | 10 |
| MaxAllowedPhaseOffset | 300 |
| MaxNegPhaseCorrection | 54,000 (15 hours) |
| MaxPollInterval | 15 |
| MaxPosPhaseCorrection | 54,000 (15 hours) |
| MinPollInterval | 10 |
| PhaseCorrectRate | 7 |
| PollAdjustFactor | 5 |
| SpikeWatchPeriod | 90 |
| UpdateInterval | 100 |
Windows NTP Client settings
These are the Windows NTP client settings and default values for the Windows Time service. These settings are contained in the Configure Windows NTP Client GPO in Local Group Policy Editor.
| Group Policy setting | Default value |
|---|---|
| NtpServer | time.windows.com, 0x1 |
| Type | NT5DS - Used for domain-joined computers NTP - Used for non-domain-joined computers |
| CrossSiteSyncFlags | 2 |
| ResolvePeerBackoffMinutes | 15 |
| ResolvePeerBackoffMaxTimes | 7 |
| SpecialPollInterval | 3,600 |
| EventLogFlags | 0 |
Note
If you use Group Policy to set the NtpServer value as part of the Configure Windows NTPClient policy and apply it to a domain member, the Windows Time Service will not use theNtpServer Registry value. To view your NTP configuration, open a Command Prompt and runw32tm /query /configuration.
See RFC 1305 - Network Time Protocol of the Internet Engineering Task Force (IETF).
FAQs
How many NTP servers should I use? ›
Have at least four NTP servers. Each network system should have at least four NTP servers, and preferably more.
Should I turn on Windows time Service? ›Every computer that is running the Windows Time service uses the service to maintain the most accurate time. Computers that are members of a domain act as a time client by default, therefore, in most cases it is not necessary to configure the Windows Time Service.
Why i am unable to start Windows time service? ›If Windows Time service isn't running, the problem might be your file corruption. Sometimes your system files can get corrupted and that can lead to this and many other errors. To fix the problem, you need to perform an SFC scan. Once the SFC scan is finished, check if the problem is still there.
What is the most accurate time server for windows? ›The NIST – the U.S. Department of Commerce's National Institute of Standards and Technology – is the primary source for synchronizing time systems in the U.S. Its servers can be found throughout the country and are most directly updated from the NIST atomic clocks.
How often does NTP sync windows? ›The date time of your PC (specific for windows) sync with one of the listed NTP server. This time sync happens every 7 days and with time.windows.com by default. You can also manually sync or update your time.
What triggers Windows time Service? ›The Windows Time service on a workgroup computer isn't started automatically at system startup by the Trigger-Start service. However, the Windows Time service is started by the Time Synchronization setting. The setting is registered on the Task Scheduler Library at 01:00 a.m. every Sunday for Time Synchronization.
What Windows 10 services should I disable? ›- Disable Windows Defender. ...
- Windows Mobile Hotspot Service. ...
- Print Spooler. ...
- Fax Service. ...
- Downloaded Maps Manager. ...
- Windows 10 Security Center. ...
- Certificate Propagation Service. ...
- Universal Telemetry Client (UTC)
Windows 10 services are important components to maintain the smooth running of your computer. However, not all of them are necessary for you. You can disable unnecessary service in Windows 10 to improve your computer performance.
How do I force Windows to resync the time? ›- Open Settings > Time & Language > Date & Time.
- Under Synchronize your time, tap on sync now. This option forces your PC to sync with the time server.
- In the File Explorer, navigate to: Control Panel\System and Security\Administrative Tools.
- Double-click Services.
- In the Services list, right-click on Windows Time and configure the following settings: Startup type: Automatic. Service Status: Start. OK.
How do I troubleshoot NTP issues? ›
NTP Authentication issues: NTP supports authentication, client and server need to use the same settings. Time offset too high: When the time offset between client/server is too large it will take a very long time to synchronize. Stratum level too high: The stratum level is between 1 (best) and 15 (worst).
How do I restart Windows time Service? ›- Restart the time service net stop w32time net start w32time.
- Resync the time w32tm /resync.
- Verify your sync status w32tm /query /status.
- To start a service, type: net start ServiceName.
- To stop a service, type: net stop ServiceName.
- To pause a service, type: net pause ServiceName.
- To resume a service, type: net continue ServiceName.
- Find out the Service Name. To do this, go into services and double click on the service which has stuck. Make a note of the “Service Name”.
- Find out the PID of the service. Open a command prompt and type in: sc queryex [servicename] ...
- Kill the PID.
In most cases it's best to use pool.ntp.org to find an NTP server (or 0.pool.ntp.org, 1.pool.ntp.org, etc if you need multiple server names). The system will try finding the closest available servers for you.
How accurate is windows time service? ›Under the right operating conditions, systems running Windows 10 or Windows Server 2016 and newer releases can deliver 1 second, 50 ms (milliseconds), or 1 ms accuracy.
How do I know if my w32tm is running? ›To check if w32time is running, do the following: go to Control Panel->Administrative Tools->Services. Scroll to "Windows Time" feature and check its "Status", which should be on "running". Check also the "Startup Type" and set it to "Automatic" or "Manual" if possible.
How do I know if NTP is out of sync? ›...
exit status of ntpstat command
- If exit status 0 – Clock is synchronised.
- exit status 1 – Clock is not synchronised.
- exit status 2 – If clock state is indeterminant, for example if ntpd is not contactable.
You can synchronize time with online server for such accuracy. Navigate to Control Panel > Clock, Language and Region > Date and time > Set the time and date > Internet time > Change settings > check Synchronize with an Internet time server and click Update now. Let us know if this helps!
How long should NTP take to sync? ›Usually it takes about five minutes (five good samples) until a NTP server is accepted as synchronization source. Interestingly, this is also true for local reference clocks that have no delay at all by definition.
Why does Windows time keep changing? ›
The clock in your Windows computer can be configured to sync with an Internet time server, which can be useful as it ensures your clock stays accurate. In cases where your date or time keeps changing from what you've previously set it to, it is likely that your computer is syncing with a time server.
How does Windows time Service work? ›The Windows Time service uses the Network Time Protocol (NTP) to synchronize computer clocks on the network. NTP ensures that an accurate clock value, or timestamp, can be assigned to network validation and resource access requests.
How do I know if my NTP server is working? ›- Hold the windows key and press X to bring up the Power User menu.
- Select Command Prompt.
- In the command prompt window, enter w32tm /query /peers.
- Check that an entry is shown for each of the servers listed above.
- The Print Spooler. Do you have a printer? ...
- Windows Image Acquisition. ...
- Fax Services. ...
- Bluetooth. ...
- Windows Search. ...
- Windows Error Reporting. ...
- Windows Insider Service. ...
- Remote Desktop.
Ensure that you don't disable critical services that are important for your device to work properly. Disabling such services can also get you locked out of your device. Quit all applications. Choose Start > Run, and type msconfig in the Open box.
What programs are unnecessary on Windows 10? ›- CCleaner.
- QuickTime.
- uTorrent.
- Adobe Flash Player and Shockwave Player.
- Microsoft Silverlight.
- Toolbars and browser extensions.
- Java.
- Pre-installed apps by manufacturers.
- Turn off the Print Spooler. When was the last time you printed something directly from your computer? ...
- Shut down fax services. ...
- Turn off Bluetooth. ...
- End remote desktop services. ...
- Touch keyboard & handwriting panel services.
Why turn off unnecessary services? Many computer break-ins are a result of people taking advantage of security holes or problems with these programs. The more services that are running on your computer, the more opportunities there are for others to use them, break into or take control of your computer through them.
Does disabling Superfetch increase performance? ›Though Superfetch is usually helpful, sometimes it can slow down your PC. As a background service, Superfetch constantly uses some CPU and RAM resources. Try disabling Superfetch if you encounter these issues.
How to reset time using cmd? ›Type "time" into the command prompt window and press "Enter." The current time setting will now display. To change it, type the proper time into the window in the "00:00:00" 24-hour format -- for example, "13:30:00" for 1:30 p.m. -- and press "Enter." The new time will now be saved.
Why is my up time not resetting? ›
That's because you have Fast Startup enabled - it's a hybrid between completely powering off the computer and keeping some important system files cached for faster startup. So when you shut down, it doesn't completely shut down, which is why the uptime counter doesn't reset after you shut down.
How do I fix Date and time not syncing? ›- Press the Windows. + R keys to open Run command box.
- Type services. msc and click OK to launch Services.
- Locate Windows Time among the services, if it is running, right-click and Restart the service. ...
- Now check if the time is automatically synced.
- Run W32tm.exe. In the Windows search bar, enter cmd. ...
- Set client to use two time servers. ...
- Set client to sync time automatically from a domain source. ...
- Check client time configuration. ...
- Configure computer clock reset. ...
- Config entries.
The Windows Time service, also known as W32Time, synchronizes the date and time for all computers running in an AD DS domain. Time synchronization is critical for the proper operation of many Windows services and line-of-business applications.
Why is NTP not syncing? ›When the NTP server is not synchronizing correctly, it may be caused by incorrect NTP configuration or a communication issue with a valid NTP peer server. This article explains how to identify the cause of the NTP issue using a TCPDUMP capture analyzed in Wireshark.
How do I troubleshoot NTP on Windows? ›- Click Start, click Run, type cmd, and then press ENTER.
- At the command prompt, type the following commands in the given order. After you type each command, press ENTER. w32tm /config /manualpeerlist: NTP_server_IP_Address, 0x8 /syncfromflags: MANUAL. net stop w32time. net start w32time.
If it can't reach any of the defined external time servers it will just keep on with its own clock. The clients will check with the DC to correct their time. So without an external source, they time will still be consistent with each other, even if it's off from the actual time.
How do I run a Windows service manually? ›...
To start a service on Windows 10, use these steps:
- Open Start.
- Search for Services and click the top result to open the console.
- Double-click the service that you intend to stop.
- Click the Start button.
- Click Start.
- Click the power button icon.
- Press and hold down the Shift key and then click Restart. ...
- Select Troubleshoot.
- Go to Advanced Options > Startup Repair.
- After the startup repair process is complete, reboot the computer.
- From the Visual Studio File menu, select New > Project (or press Ctrl + Shift + N ) to open the New Project window.
- Find and select the Windows Service (. NET Framework) project template. Note. ...
- For Name, enter MyNewService, and then select OK. The Design tab appears (Service1. cs [Design] or Service1.
How do I stop a service from being stuck in stopping state? ›
- Find out the Service Name. To do this, go in to services and double click on the service which has stuck. ...
- Find out the PID of the service. Open an elevated command prompt and type in: ...
- Kill the PID. ...
- Video Tutorial – How to Kill A Service which is Stuck at Stopping.
- Use Windows 10 Update Assistant to help you install the latest updates. For more info, see Windows 10 Update Assistant.
- Reinstall Windows 10 to return your PC to a cleaner state and try to fix issues. For instructions, see Reinstall Windows 10.
- Check the BIOS. You need to check for two things in the BIOS. ...
- Reset the BIOS. ...
- Fix the Boot Records. ...
- Enable or Disable UEFI Secure Boot. ...
- Activate the Windows Partition. ...
- Use Easy Recovery Essentials. ...
- Reinstall your Windows.
Recommended Configuration
It is NOT recommended to use only two NTP servers. Also refer to the upstream NTP documentation for additional detail: 5.3.
The more clocks you have showing the same time, the more sure you can be that they are right and that any clock showing a different time is incorrect. The same principle holds true for getting time over the Network Time Protocol (NTP). If your client allows it, you should connect to multiple NTP servers.
Which NTP servers should I use? ›In most cases it's best to use pool.ntp.org to find an NTP server (or 0.pool.ntp.org, 1.pool.ntp.org, etc if you need multiple server names). The system will try finding the closest available servers for you.
When should I use multiple servers? ›A multi-server environment can be more cost-effective than a single-server environment. By using multiple servers, you can spread the cost over multiple devices. In addition, you can use lower-cost hardware using multiple servers than you would in a single-server environment.
Which time server is most accurate? ›Often, the time signal uses a standard such as UTC (Universal Coordinated Time), derived from atomic clocks or GPS (Global Positioning System) service. Atomic clocks are the most accurate sources of time available.
Does NTP work without Internet? ›Typically, devices rely on an internet time server and a clock source, such as a GPS satellite, to synchronize time across devices. However, in an offline scenario, where devices are not connected to the internet, time synchronization must be achieved via a local Network Time Protocol (NTP) server.
What is the NTP server IP address? ›| Name | IP Address | Status |
|---|---|---|
| ntp-b.nist.gov | 132.163.96.5 | Authenticated service |
| ntp-wwv.nist.gov | 132.163.97.5 | Authenticated service |
| ntp-c.colorado.edu | 128.138.141.177 | Authenticated service |
| ntp-d.nist.gov | 129.6.15.32 | Authenticated service |
What ports does NTP use? ›
NTP is a built-on UDP, where port 123 is used for NTP server communication and NTP clients use port 1023 (for example, a desktop).
How do I check my NTP status? ›- Click Start. Type "cmd" into the text box and press "Enter." The command utility will appear.
- Type the following: NET TIME \YourServer /SET /YES. ...
- Alter the time on the server to any time and make a note of it.
- Check the time on your client computer.
NTP normally uses multiple time servers to verify the time and then controls the slew rate of the system. The algorithm determines if the values are accurate using several methods, including fudge factors and identifying time servers that don't agree with the other time servers.
Is NTP still being used? ›NTP is implemented in the majority of Linux and Windows based operating systems, widely used in the control systems.
How accurate is NTP time sync? ›NTP can usually maintain time to within tens of milliseconds over the public Internet, and can achieve better than one millisecond accuracy in local area networks under ideal conditions. Asymmetric routes and network congestion can cause errors of 100 ms or more.
How do I sync my NTP server with time? ›- Open a command prompt.
- Check time sync: w32tm /query /source. ...
- List NTP server list: w32tm /query /peers. ...
- Update the peer list: w32tm /config /update /manualpeerlist:SPACE_LIMITED_NTP_SERVERS /syncfromflags:manual /reliable:yes.
- Force sync: ...
- Check if the server is now using NTP:
There are many types of servers, including web servers, mail servers, and virtual servers.
What are the 3 most important things as a server? ›- A good memory. This is probably the most important skill for a server. ...
- Great customer service skills. As a server, you are the face of the restaurant. ...
- The ability to multitask. As a server, you will often be doing several things at once. ...
- A positive attitude.
Measure the number of requests made to the server during a given period and then multiply that by that amount of power needed for the server's tasks. If you don't have a server of your own to reference, you can use your market research or study similar servers used by other businesses.