Consistent Time

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The Consistent Time Integration Profile (CT) provides a means to ensure that the system clocks and time stamps of the many computers in a network are well synchronized. This profile specifies synchronization with a median error less than 1 second. This is sufficient for most purposes.


The Consistent Time Integration Profile defines mechanisms to synchronize the time base between multiple actors and computers.


Various infrastructure, security, and acquisition profiles require use of a consistent time base on multiple computers, to synchronize logs, authenticate users, digitally sign documents, et cetera.


The Consistent Time profile requires the use of the Network Time Protocol (NTP) defined in RFC 1305. When the Time Server is grouped with a Time Client to obtain time from a higher tier Time Server, the Time Client shall utilize NTP. For some Time Clients that are not grouped with a Time Server, SNTP (see RFC 4330) may be usable.

Windows Client Configuration

To configure Windows system to be a time client, simply enter the following at the command line:

C:\> net time /setsntp:hostname

Where hostname is the host name or IP address of the time server.

To ensure that your clock is updated immediately, stop the windows time service, set your clock back 5 minutes, then set the hostname, and restart your time service.

C:\> net stop w32time
C:\> time
C:\> net time /setsntp:hostname
C:\> net start w32time

Unix Client Configuration

On a unix system, ask a sysadmin to ensure that ntpd is running and configured properly. Typically, this involves ensuring that /etc/ntp.conf contains the following line:

 server hostname

Where hostname is the host name or IP address of the time server.

Systems Affected





IHE IT Infrastructure Technical Framework Version 1 or later

  • Vol. 1 - Section 7
  • Vol. 2 - Sections 3.1

Underlying Standards:

  • NTP Network Time Protocol Version 3. RFC1305
  • SNTP Simple Network Time Protocol (SNTP) RFC2030

See Also

Profile Status: Final Text

The IT Infrastructure Framework is the official master document for this Profile.

The Network Time Protocol is a site providing an open source implementation of the NTP protocol.

NIST provides several time servers in the US that can be used to synchronize a system's internal clock. is the international pool of NTP servers set up to distribute and share the load on time servers.

The CT FAQ answers typical questions about what the Profile does.

This page is based on the Profile Template