Share via

SNTP Registry Settings

Other versions of this page are also available for the following:

Windows Mobile Not SupportedWindows Embedded CE Supported


The SNTP registry settings are located under the HKEY_LOCAL_MACHINE\Services\Timesvc registry key. Upon system startup, services.exe uses the information located under this key to initialize the SNTP service.

After you have modified the registry settings for your SNTP service, it is not necessary that you reboot your device for the changes to take effect. To implement the changes in the registry without rebooting the device, you must pass in the IOCTL_SERVICE_REFRESH IOCTL to the xxx_IOControl (Services.exe) function. This is described in the Configuring the SNTP Service topic.

The following table shows the named values for the HKEY_LOCAL_MACHINE\Services\Timesvc registry key.

Value : type Description


Specifies the domain name of the SNTP server. If the name of one server is specified, this value is type REG_SZ. If a list of servers is specified, this value is type REG_MULTI_SZ. If no name is provided, server-only operation will be assumed.

> [!NOTE] > For a list of available SNTP servers, visit this Microsoft Web site.

Refresh : REG_DWORD

Specifies the period, in milliseconds, between synchronizations with the SNTP server. This is ignored in server-only mode.

RecoveryRefresh : REG_DWORD

Specifies the time, in milliseconds, until next synchronization if the previous attempt failed. This is ignored in server-only mode.

> [!NOTE] > The time specified for this key must be less than the time specified for the Refresh key.

Threshold : REG_DWORD

Specifies the interval, in milliseconds, between the time on the SNTP server and the current time. If the difference between the SNTP server time and the local system time is larger, the update is ignored unless the system clock is presumed incorrect. This is ignored in server-only mode.

ServerRole : REG_DWORD

Default set to zero (0). Specifies the time server role. If this value is set to 1, a time server running on the Windows Embedded CE-based device will be enabled.

Trustlocalclock : REG_DWORD

Default set to 1. If this value is set to zero (0), the system is presumed not to have Real-time Communication (RTC) capabilities. If this is the case, server multicast is disabled until the clock synchronization with the SNTP server succeeds, and queries to the server return the "unreliable clock" flag. Also, time synchronization is forced on system wake-up.

If the client is disabled, the clock is presumed to be privileged and this value is ignored.

Multicast : REG_DWORD

Specifies the address or addresses for multicast mode.

If the value is a REG_DWORD, it indicates a 32 bit value representing the address as an IPv4 address.

If the value is a REG_SZ, it indicates a string containing a host name.

If the value is a REG_MULTI_SZ, it indicates a list of strings containing multiple host names.

Multicastperiod : REG_DWORD

Specifies the interval, in milliseconds, between subsequent multicasts.

Enable automatic daylight savings switch-over

The HKEY_LOCAL_MACHINE\Software\Microsoft\Clock\AutoDST registry subkey enables the SNTP service (timesvc.dll) to perform automatic daylight savings switch-over.


Timesvc.dll is not included on all Windows Embedded CE powered devices.

Table below shows the named value for this subkey.

Value : type Description


Default setting is 1, which enables the automatic daylight savings switch-over service. Setting of 0 disables the service.


Both SNTP and NTP are clients of the User Datagram Protocol (UDP). The UDP port number assigned to NTP is 123.

See Also


xxx_IOControl (Services.exe)


Configuring the SNTP Service