Synchronizing your computer clock to an atomic clock

After digging around on Google for ideas, I ran across this URL:

Windows 2000 now includes a built-in time service which is similar to TimeServ.

Time Server is a service for NT which is available on the Windows NT Resource Kit CD. It consists of TIMESERV.EXE, TIMESERV.DLL and TIMESERV.INI.

Installation
To install the service, simply copy the EXE and DLL files into the \WINNT\SYSTEM32 directory and run TIMESERV -AUTOMATIC (if you want to register the service and have it start automatically after each reboot) or TIMESERV -MANUAL (if you want to register the service but have it started manually).

Configuration To configure the time server, you must edit the INI file TIMESERV.INI in the WINNT (not SYSTEM32!) directory. It is currently setup for use on a secondary time server, meaning that it gets its time from another computer but does not provide that time to any other computer.

There are many parameters in the INI file. The most important ones are:

• Type - The type of time server that this computer is (usually SECONDARY);
• PrimarySource - The computer which is the time server source for this computer;
• Period - the number of times during a day that this computer should synchronize its time with the PrimarySource computer. If this value is 24, the time will be synchronized every hour. (NOTE: the time is synchronized only if the clocks differ by 0.5 seconds or more).
• Timesource - set to no if this computer is not a time server source for other computers (for Type=SECONDARY). Set to yes if this computer is a source for other computers (for Type=PRIMARY or Type=MASTER).
• Log - set to yes if this computer should write to the NT Event Log every time that it checks its time with its PrimarySource (whether or not its clock was adjusted). Set to no if this logging is not desired.

Other parameters can be left as is. Now that the INI file has been configured correctly, you must update the service to use the new configuration.

Updating the Configuration
Once the time server's INI file has been configured correctly, you will have to update the time server service to now use the new configuration. To do this, first stop the Time Server service using the Service Control Manager in the Control Panel. Once it is stopped, run TIMESERV -UPDATE from the Start|Run facility. After this is completed, just restart the Time Server service and, voila, your service is configured.

If you requested logging, you can now check the Event Viewer to ensure that the first synchronization succeeded. If no error message is given, your Time Server is now operational.

Full details at http://www.niceties.com/timeserv.htm

Step One
Go to Apple Menu > Control Panels > Date & Time. Make sure that the Time Zone is set correctly for a major city in your Time Zone. Since this is a setting you must choose the first time you ever turn on your Mac, or at the first boot up following an OS install, odds are good it will still be correct. Check the date too: If the year reads 1956, you have a very old Mac and the clock battery is likely dead and needs to be replaced. Regardless, set the date correctly.

Step Two for Mac OS 8.5 or later:
Make sure the box marked "Use a Network Time Server" is checked. If it isn't, check it. Close the "Date & Time" Control Panel. Now you're done.

Step Two for earlier versions of Mac OS:
Close the "Date & Time" Control Panel. Get on the Internet and download NetChronometer from http://www.kezner.net/netchrono.html and run the Installer application. Reboot. Open the NetChronometer Control Panel and make sure "Use Internet Time Server" is checked and that the other settings are as you want them, and close the Control Panel. Now you're done. You will probably want to pay Jeremy his $7.

Mac OS X

10.2 "Jaguar" or earlier
Go to Apple Menu > System Preferences > Date & Time. Select the Network Time tab and make sure the service is running (or click Start if it isn't). Check Manually Configure and enter an NTP server in the box. (There is no list to pick from like in Mac OS. For a source of NTP servers, see below.) Close the window. Now you're done. Thanks to ccunning for his contribution.

10.3 "Panther" or later
Go to Apple Menu > System Preferences > Date & Time. Under the primary tab, with the rather redundant name "Date & Time", check the box at the top of the page next to "Set date & time automatically". You may optionally select the Apple time server closest to your geographical location, or manually enter the NTP server address of your choice in the drop down box/menu to the right. Could this be any easier? Probably not.

Useful Tips
martin points out that it's usually a good idea to choose a network time server that is geographically close - or few traceroute hops away from your own computer. And you know, he's right! I myself do not use Apple's own time server. martin adds that an accurate listing of network time servers can be found here: http://www.eecis.udel.edu/~mills/ntp/servers.htm

HOWTO for most Linux distributions

• ntpdate
• hwclock

ntpdate time-a.nist.gov
hwclock --systohc

HOWTO for most Linux distributions (Revised)

There are two ways to go about setting up ntp to sync your clock to atomic clock time. The first and foremost, though, is manually, as pokey has explained.

Commands:

• ntpdate
• hwclock

And to sync the clock by hand, login as root, type the following at a shell:

Now these commands are all well and good to sync your computer's clock after it's been off for 5 months or so and it's clock is pretty dead, but the other operating systems do not force you to have to set your clock time manually, and neither should you have to. For mission critical time calculations, such as for calculating sattelite uplink speed, you must have both the times set to Atomic clock time. The Sattelite, will, of course use GPS time stamping, and the ground, will run xntpd.

Usage:
  /etc/init.d/xntpd {start|stop|restart|status}

This is a daemon controller that can be set under chkconfig, by running the following as root:
$ chkconfig --add xntpd

Finally, add the ntp servers of your choice from the list panamaus lists above to /etc/ntp/step-tickers.

Here's an example from my machine:

216.27.139.69
time.mit.edu

HOWTO for Windows XP

1. Double-click the clock in the system notification area (also known as the system tray).
2. Click the "Internet Time" tab in the Date & Time Properties dialog box.
3. Check "Automatically synchronize with an Internet time server," if it is not already checked.
4. Choose a server from the drop-down list, or type one that you know yourself.
5. Click Update Now to test the setting.
6. If it worked, good. Your clock will synchronize once a week automatically when connected to the Internet. If not, try a different server.

This should work with all NTP time servers; I've tried a few, and settled on one that's on my LAN for maximum speed. The default server is "time.microsoft.com." It is worth noting that Microsoft has set this to enabled by default as they mandate product activation within the first 30 days after you boot Windows XP.