[Haskell-cafe] Re: Computer time, independent of date

[Steve Schafer]

On Sat, 10 Jan 2009 15:04:36 +0100, you wrote:

>POSIX realtime extensions have been developed to be high reliable.

I think people are missing the details here. Yes, the built-in real-time
clocks have excellent long-term accuracy. They run UTC-based correction
algorithms using NTP, and are thus traceable to TAI. However, they offer
no guarantees on interval measurements, and the correction algorithms
can cause the measurement of a time interval of an hour or so duration
to be off by +/- 1 sec, especially within the first few hours after a
cold boot. If you care about leap seconds, you should certainly care
about that magnitude of error.

Steve Schafer
Fenestra Technologies Corp.
http://www.fenestra.com/