UNIX for Dummies Questions & Answers

So should I conclude from the correspondence that approach to a timekeeping is not consistent among various Linux flavors?

For the record, I am a "he", I have been of legal drinking age for several decades, and I wrote this a few years ago. It's a bit dated as it describes an early implemenation of NTP, but still useful (I hope).

The note has been taken!

---------- Post updated 04-20-11 at 04:24 PM ---------- Previous update was 04-19-11 at 04:51 PM ----------

I was reading that real world servers are set to use UTC and do not use timezones. Is it true?

It's generally the norm for the system clock to be UTC, and the timezone itself to be calculated from the TZ variable, or /etc/localtime, or other means.

Thanks to Corona688

And how then it takes care of summertime/wintertime, this one hour switch. I mean this "daylight savings time" and then turning back to normal.

How does anything else do it? The hardware clock isn't aware of DST!

The library call gettimeofday() checks the time of year, and adds another hour to the time it gives you accordingly. It checks TZ environment variable for the local timezone or, failing that, what zone file you've stuck into /etc/localtime.

I've been reading that timekeeping is very important to servers, especially for these running databases and that time synchronizations should be done with great precision down to few milliseconds. I don't have NTP server to try, but when you go to let say, time.gov, (I assume it is NTP server) it shows "Accurate within 0.2 seconds", which is far from been super precise (200 millisecond).
So if there are two systems on different networks to be synchronized the delta would be even bigger, I guess. Please show me where I'm wrong, or how to deal with it in general if I'm correct. I'm asking only for a general guidance, I will research and find the rest of it by myself. Just give me a direction!