[tz] tz database update on a publication & thank-you.

Paul.Koning at dell.com Paul.Koning at dell.com
Thu Jul 30 23:51:03 UTC 2020

> On Jul 30, 2020, at 6:41 PM, Robert Elz <kre at munnari.OZ.AU> wrote:
> ...
> ps: I still believe it is a big mistake to ever convert times expressed
> in local time into some other timebase, and store that, instead of storing
> the local time, and the timezone information.  The local time is the recorded
> absolute value, which will never change - even if someone later realises that
> the offset from UTC (or GMT) that's in the database happened to be incorrect
> and fixes it.   But if you've stored just the UTC (or GMT) version, you no
> longer really know whether that came from the old bad data or the new fixed
> version (especially if you're not keeping a very close watch on every change
> to the database - and even moreso if updates are automated and just happen
> without anyone really being aware of it).

True, assuming the common case where the original time reading was from a clock set to local time.  In some cases people would be using clocks set to another standard, such as GMT or the time of some other standard meridian.  If you're looking at timestamps from the chronometer era of sailing, the reference time is that of the chronometer, which is set to GMT, or Paris time, or Washington time, etc., depending on the ship.

Similarly, astronomical records might be given in GMT.  Or even local sidereal time, which really makes things fun.


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