Time Services

Title: Time Services
Applies to: Campus users requiring accurate computer time
Section: Network Services
Owner: Manager of Network Services
Last updated: 24 July 2026

Introduction
Many computers require accurate time for proper operation and coordination with other computers and users. This technical note describes the University of Regina time service and its use.

Why do we need accurate time?
All computer files are time stamped in some form and all users expect, as a minimum, time to be accurate within at least 60 seconds so that they know that the minute portion of a timestamp is reasonably accurate. Upon further analysis it turns out that users actually expect much higher accuracy as they often make important decisions based on which file is newer. If time is loosely synchronized and periodically adjusted a user might create a file, the system might move the time back 90 seconds due to a normal time synchronization check, and then the user might create a 2nd file which appears to be created before the 1st file! In a distributed network computer there are a number of other reasons for wanting accurate time:

• programs, like make under Unix, compare the timestamps of source files against object files to see if the object file needs to be recreated.
• system logs contain time stamps and it is often important that events be entered in the proper order.
• users conducting scientific experiments often timestamp data.
• some security software requires that the system time be close to Universal Coordinated Time.

While some of the reasons for accurate time given above only require accuracy to within a few seconds there is a stronger requirement that time be monotonically increasing(never goes backward). In order to ensure this, accuracy of less than approximately 120ms(depending on the system) must be kept as most systems can only slow down or speed up their clock to make a change in time that is less than 120ms.

How Accurate Time is Achieved
On the internet there are a number of computers synchronized directly to highly accurate time provided through radio broadcast services like WWV or satellite service like the Global Positioning Satellite time service. These servers run the ntp(network time protocol) code so that other computers can synchronize to them. An on-site stratum 1 server is usually provided as well so that accurate time is maintained even over the day or two it may take to repair a failed internet connection. An onsite server also reduces the network load and the load placed on heavily used internet stratum 1 servers.
Time service at the University of Regina will be provided by synchronizing to a local stratum 1 server and stratum 1 servers on the internet. See Appendix A for a description of the server configuration.

Synchronizing client computers

LINUX
Almost all Linux distributions use chronyd by default and are configured to use a pool of internet time servers. If you require higher accuracy and independence from internet outages you can configure custom local time servers from the list in Appendix A. 

Macintosh Users
MacOS is configured by default to synchronize time to internet time servers.

Windows Users
The service w32time included in Windows is used to synchronize time and is configured by default to. If you require higher accuracy and independence from internet outages you can configure custom local time servers from the list in Appendix A.  These changes require administrator privileges.

Conclusion
Accurate time service is available to University of Regina users who require higher accurancy and/or independence from internet outages.

References
David Mills et. al., "Network Time Protocol Version 4: Protocol and Algorithms Specification", published as internet RFC5905

Appendix A - Server Configuration

The ntp software daemon, ntpd, runs primarily on Linux machines so it is installed on sue.cc.uregina.ca, atlas.cc.uregina.ca, hypnos.cs.uregina.ca and clock.uregina.ca. Clock.uregina.ca provides stratum 1 time service via a GPS clock to the other servers and shouldn't be used directly.This provides redundancy in the case that one of the three machines is down for servicing or the network segment that one of them is on is down. Each of these is synchronized with two stratum 1 servers and one stratum 2 server.This will provide stratum 2 service to the U of R derived from six independent stratum 1 servers for reliability.

To allow flexibility in changing machines the following CNAMES are used:

Access to on campus users is unrestricted. CA*net users may also sync to timelord.uregina.ca as long as only 1 or 2 hosts per site synchronize.

Users should always use the timelord aliases as the names of the machines providing the service are subject to change without notice.

Revision History
v0, 1996-07-22, Initial version
v1, 1996-07-22, updated winsntp link
v2, 1998-03-22, added ntpdate for Solaris, removed Banyan ref, replaced wsntp with d4time, timelord2 changed to atlas
v3, 2001-04-16, updated to reflect local stratum 1(clock.uregina.ca), added section for Netware 4/5 servers, changed Macintosh users to use the built-in apple client instead of tardis
v4, 2002-04-21, updated ntp software link, remove MSDOS/Ultrix/OSF1 section,removed reference to CS providing tardis time services.
v5, 2003-10-01, added section for WinXP using w32time.
v6, 2008-09-02, updated WinXP section for w32tm instead of w32time.
v8, 2010-02-10, updated WinXP section to include three servers in client mode as suggested by Ryan Goolevitch
v9, 2015-11-05, updated Unix section to remove SunOS and add reference to ntpdate/sntp. Update macintosh section. Remove Netware/Windows 98.
v10, 2026-07-24 updated to current versions and simplified to reflect default automatic configurations.