12Ghosts.com | Download | Order | Support 

12Ghosts Sync

12Ghosts - Sync


What does it do for me?

Synchronize your computer time over the Internet with an atomic clock. This can be done automatically and completely unnoticed. (A log file is created about all activities so you may verify that it did what it should and by how much your clock was adjusted.

Choose out of a large list of reliable time servers on the Internet or add as many servers near your location. Adjustment can be done automatically between once every second to once a month. The program waits for an Internet connection before doing anything, then adjusts your clock to radio precision, without necessary interaction.

Supports S-NTP version 4 time protocol for a precision of up to one millisecond. The synchronization over HTTP port 80 and a proxy server is possible. Command line parameter to set the time only once.


Where should I start?

Choose one or more time servers near you. The nearer it is, the higher the probability that you get a precise time. Then click Sync Now.

The first time you synchromize, you may be asked to start the 12Ghosts Synchronize service, and stop the Windows Time service. Administrator rights (or elevation) is required to start the service. This needs to be done only once at the first start.


Server Pool

A good idea is using the NTP time server pool. This is very long list of time servers worldwide. Every time you contact pool.ntp.org you are actually transfered to a different server, so you don't depend one one server alone. You may prepend the address with your country code to make sure you only get servers near you, for example:



Configure your firewall

Your firewall needs to allow 12sync.exe access to UDP port 123 (NTP, Network Time Protocol), outbound and inbound. However, only to one specific address: the time server(s) you have selected. You also need to give it access to UDP port 53 (DNS, Domain Name System) to resolve a domain name to an IP address. But this should be set automatically.



Don't sync automatically too often. This will not enhance the accuracy since each adjustment may introduce unsteady values. Instead, use the speed options to adjust your clock speed. A value of 8 hours is probably good enough. Windows, for example, has a default of one week.

It is recommend to let the program Ask for confirmation if the time differs by more than 60 seconds. Your computer may be wrong by a second or two a day, so it is highly unlikely that a correction of 60 seconds is necessary. Rather, the time server may be wrong.

In the Speed tab it is recommended to limit round-trip delays to 200-300 ms. (Note, you may right-click on any option for a short explanation.)

Don't change the time protocol, NTP is most precise. Unless, if you need to use a proxy server you may need to choose the HTTP protocol. Enter the same proxy settings as in your browser.


Precision of Internet Time Servers (Advanced)

There are certain limits to the precision of setting the time. You should be able to set the time exactly down to one tenth of a second (100 milliseconds), or maybe even one hundredth of a second (10 milliseconds), though.

Windows "only" allows to set the time exactly to one millisecond. That is, no matter how precise you try to set your clock, it won't get better than that. Forthermore, even if you're located pretty much next to a caesium atomic clock, Internet delays and network traffic will hardly allow you to receive a response any faster than within 4-5 milliseconds. Since it is not entirely clear if the delay happened outbound or on the way back, one can only estimate that the response was sent at about half the round-trip delay. You'd be lucky to set the time down to 2-3 milliseconds, that way.

Finally, most computer mainboards these days have a clock build in that has a resolution of 15 ms. In other words, if a clock program asks for the "current" time, it will always get the time of the most recent 15 ms step. No more.

In short, it usually doesn't matter how precise the time server is that you synchronize with. They are all in a range of a few milliseconds, which is more than what you can use. A caesium (CS) atomic clock is considered to be the very source of exact time. GPS or DCF bound time servers, however, get a radio signal from caesium atomic clock within almost "no time", so they can be considered to be as strong.


Clock Speed (Advanced)

That said, you can now start enhancing your own clock accuracy. Your PC hardware clock may just not be configured correctly. In the Speed tab check Change PC clock speed. This uses the adjustment and the time last synchronized to calculate a more precise increase per clock interupt. For the accuracy to increase and stabilize, set the percentage to a low value of 5-10%.

This is all you need to do, unless you really want to figure out what all this is about:

Let the program work automatically for a few days, then check the log file. It will show the exact speed it has determined. If you see a convergence to a particular value you may use that to set the clock interupt increase to that fixed value. It is given in 100 ns steps, that is, 15.6250 ms (64 interrupts per second) are 156250. Changing this by only 1 digit adjusts the speed by 6400 ns per second, or about one second in two days (43,4 hours).


Messages and Log File

If you have set the program to sync automatically, you may still verify what happened when. Turn off Always display confirmation and error messages and check Create log file instead.

Limit the log file by size or a certain number of days, for example 200 KB or 14 days. You may choose to log only adjustments that exceed a certain value.

(For admins: In the log file path you may use %COMPUTER-NAME%. This will be replaced automatically, so you may have 12-Sync create different log files for each client in the same folder on a central server.)


Command Line Parameters

12-Synchronize supports the following command line options:

/once       Synchronize once and then stop. Otherwise 12-Sync will stay in memory, showing a tray icon, and synchronize at the selected interval.
/s Start silently and reside in the taskbar tray.


12Ghosts Power Tools

© 1993-2014 12Ghosts Inc. All rights reserved.