Setting up a Time Service.
The first question is 'Why bother ?'
Well, if you are going to save files to a Home Server / NAS, sooner or later you are going to want to know which file is the 'latest' version - the one on your computer or the one on the Server. Unless both are using the same Time source doubt will exist.
Of course having the exact correct time is vital for those wishing to locate and observe fast moving astronomical objects, such as near earth comets & asteroids or the International Space Station, with a computer controlled telescope.
Windows allows you to set up a 'basic' Time service on whatever computer you choose, however this means you have to open a 'hole' in your firewall. Fortunately a 'shareware' utility exists (with the name 'TARDIS') that is able to fetch the time using HTTP protocols (so no need to open ports) = see later.
How do I setup Microsoft Windows Time ?
This is setup via Start, Settings, Control Panel, Date & time, Internet time tab. It will typically maintain the correct time to within +/- 1 or 2 seconds (Windows security depends on the time between 2 computers wishing to connect to one-another (eg via a 'Map network drive') being no more than 5 seconds out).
When enabled via Date & Time, the Windows Time service (w32time) will be run and connect to an Internet Time source using (Simple) Network Time Protocol (SNTP). This protocol uses UDP port 123. This requires you to open a 'hole' in both your software firewall and your Router firewall.
You can check in the Event Viewer that Time is being updated OK
Why isn't the Time being updated ?
If you are using Windows XP sp3 built in Windows Firewall, select the Exceptions tab, add your Windows Time software, then click 'Add Port', enter the port name (eg. NTP), set the port number to 123 and set the type to 'UDP'.
In the free version of Zone Alarm, you will have to add the IP address of the NTP Server to your 'Trusted' Zone (free Zone Alarm does not allow you to specify ports) - you can find the IP from 'Alerts & Logs' (look for UDP link to IP:port 123 being blocked).
My Firewall is passing UDP123 OK, but Time is still not being updated ?
Many Routers will automatically allow w32time NTP (UDP 123) requests to pass through without problem. If yours is one that blocks these requests, you will typically be able to 'open' the port via some 'port forwarding' or 'port enable/disable' menu (see your Routers manual). If you are still unable to get access to a NTP Time Server on the Internet via UDP123, you will have to use a non-Microsoft solution (see later)
Your_computer/s unable to reach the Router (eg your Server / NAS) can fetch the Time from a computer that can. For details see below :-
How do I setup my own Windows Time Server ?
UDP123 is unreachable - is there anything else I can do ?
Yes = there are 3rd party applications that are able to fetch the time using Internet (http:) protocols and then 'forward the time by acting as a UDP123 Service.
'TARDIS' is one that can be set to fetch the time using HTTP. HOWEVER it does so by connecting to a website (that you specify) which is ASSUMED to have the correct time. The problem here is not only the HTTP delay but also the fact that your chosen web site might not actually be maintaining the correct time at all. You should thus use HTTP ONLY if you have no other choice.
TARDIS (on UDP123) will maintain better accuracy that Microsoft Windows w32time (since it correctly implements NTP 'round trip delay' adjustments etc). This is only vital if you are performing astronomical observations that you wish to submit for peer review etc.
At least one computer should be set up using the TARDIS software to fetch the Time from the Internet and re-broadcast it across your local ('Trusted') LAN. Assuming your personal computer is connected to both the Router (Internet) and Server / NAS sub-nets, this should be used as the Time source. As a 'back-up', you should also install TARDIS on your server, however you should set it to fetch the time from your own PC (and not broadcast).
All the other computers on your LAN can use the 'K9' utility to set their time correctly.
On all computers using TARDIS/K9, the Windows time service (w32time) should be located and Disabled. If you don't, it may get upset and fill your Event Log with complaints about port UDP123.
What about Time Zones ?
NTP Time is 'GMT Time'. You most likely use British Time (i.e. Summer/Winter time). So make sure you have set the 'Automatically Adjust for Daylight Savings' in Time Zone tab of the "Date and Time" applet (in the Control Panel, or by double clicking on the task bar time (assuming you have selected 'Show the clock' on your Desktop)), otherwise you may find your computers are 1 hour 'out' :-).
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