storing timestamp data

Markus Kuhn Markus.Kuhn at
Wed Mar 31 14:37:53 UTC 1999

Lee Geoff wrote on 1999-03-31 13:45 UTC:
> I'm interested in storing date/time data in Ingres
> databases which are running on Unix servers. We are recording timed events
> on Unix servers as well as Windows 3.1 and NT PCs.  I have had problems with
> the apparent miss-handling of data when viewed before or after a DST
> transition. Can anyone point me at words of wisdom or good advice?

Words of advice: Store timestamps always in UTC. Make sure all your
machines know UTC reliably. This is usually not a problem under Unix,
where UTC is the native time zone on which all kernel time information
is based (local times are only a convenience display option provided by
application software), and where network protocols such as NTP are
commonly used to keep the kernel clock and the official UTC in sync
better than 10 ms. The problem are occasionally platforms such as those
produced by some hacking firm in Redmond with too much market share,
which insist on keeping the hardware clock in local time and derives UTC
from this by user configuration. These systems are inherently prone to
failure, especially around DST switches (see the annual comp.risks
discussion of this every fall).


Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at,  WWW: <>

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