[SOLVED] How important is it that system clock is in time?

[Trikki]

Couple of questions about time and clock accuracy. I guess this is not necessarily related only to Mageia, but I just don't seem to find a clear answer to this from anywhere.

Short background is that I have an oldish computer that just does not seem to keep time anymore that well, it gets couple minutes behind within a week or so. I have already changed the bios battery, but it made no difference (well maybe it made it a bit better, but still not accurate enough). But as I have seen no problems caused by the inaccurate clock, I would like to ask a couple of general guestions:

How important is it that the clock of a computer is exactly on time?

What is the actual harm if a computer clock is not exactly in time? (Say that it is five minutes ahead or fifteen minutes behind?) What are the dangers in this?

I have looked into using NTP, but if I understand correctly I migh need to change my router settings for that to work (as my routers firewall migh block the ntp server by default?). But the few minutes of incorrectness in the computers clock really does not bother me much, so if it is not anykind of a real problem I am wondering if it is worth to bother with the whole thing?

[wintpe]

you are quite right that for a typical home user the accuracy of the clock is not that
important to the operation of a workstation class desktop.

in a banking environment that i work in the accuracy of the time stamping of logs, or the time stamping of trades is of paramount importance for regulatory reasons.

also any one that uses the kerberos authentication system, needs to ensure that there systems are within a few seconds of accuracy
otherwise the authentication system stops working.

ntp uses port 123 over udp mostly, although it can choose to use tcp, but this can use up a whole loads of connections in a large estate hence why udp is the better choice overall.

usually your router will block incoming connections simply because its on an unroutable network, assuming that you have a consumer grade adsl router, and all outbound connections are usualy allowed via NAT.

if you are using something like me , ie a wan to wan router and firewall, then perhaps you are blocking NTP, but it would be unusual for that to be blocked in the default equipment supplied by ISP's.

config of NTP in mageia , at least under kde is such a dodle, anyone can do it, and its hooked into the time app in the task bar.

regards peter

[Trikki]

Thanks for the answer!

It really does not sound so difficult so, maybe I'll just use the NTP, then I won't have to worry about it.


EDIT.
(Ps. Note: As I marked this [SOLVED] I had to remove the word "exactly" from the original subject-name, because I could only ad three more characters to the original title)

[benmc]

Hi Trikki

just another take.
If you are using the flash-plugin to watch on-demand services - e.g tv programmes that have an expiry date, they can can be peculiar about the time as well. A few 10's of seconds seems to be ok but if your clock is out by a even few minutes there can be issues as well.

[Trikki]

Thank you, that's good point, I didn't even think of that - I do watch a lot of programs that have a time limit.

Anyways I now have the NTP set up, so the clock should be always in time. It was really easy to set up, no problem at all.