[tz] What is LMTZ?

Clive D.W. Feather clive at davros.org
Fri Sep 20 09:25:05 UTC 2013

Guy Harris said:
> Does anybody else believe the tzdb should handle the history of 12-hour vs. 24-hour clocks or of pre-standardized-time timekeeping other than recording when standardized time was adopted?  If not, I don't see any point in further discussion of those topics on the tz list.

On the contrary, I don't even see how it's possible.

There's no UK legislation that I'm aware of on the topic. I know that
British Rail, Southend-on-Sea Corporation Transport, and Midland Red Bus
all changed from 12-hour to 24-hour clocks in their published timetables in
different years. Since there were scores if not hundreds of other transport
companies in England alone, that's a huge amount of data that will never be

And if one shop puts "open 9 to 6" on its sign while the one next door puts
"Hours: 0800 to 1730", do we need to keep a record of that?

The idea of itself is ridiculous.

>>> I don't think changes to calendars before the adoption of standard time (as was the case for the adoption of the Gregorian calendar in Western countries) belong in the tzdb.  *Perhaps* the changes from the Julian to the Gregorian calendar *after* the adoption of standard time belong in the tzdb, if there are any, should be recorded in the tzdb,

What about the adoption of other calendars? Didn't Sri Lanka spend some
time on some other calendar?

No, I don't believe this belongs in tzdb. It's interesting information, but
that is *NOT* where it belongs.

> I don't think the time related material in the tzdb should go back before the establishment of standard time, for some meaning of "establishment", whether it means "adoption of standard time nationwide as civil time" or something looser.

Agreed. And it should be further limited to information about the mapping
from local standard time to UT (in the loose sense).

> If somebody wants to establish a Big Database of all changes in time and date reckoning, not just establishment of standard time and rules for changes from standard time, I have no problem with them doing so; I just don't think the tzdb should be that database, even if whoever establishes that database chooses to use the tzdb as part of their database (thus becoming a user of the database).


> 	In the long term, think that the tz project should attempt to provide as much high-quality data as is reasonably feasible, and that users of the tz data should have the ability to "winnow" and install only a subset of the data.  Here, users of the tz data includes OS vendors, appliance vendors, other software projects, software packagers, system administrators, and end users.
> so that the tzdb can have historical data about standardized time *but* should offer tools to allow users, in his sense, to discard historical data if it imposes what those users deem significant costs in excess of what they deem the benefits.

I think this is a good objective.

Clive D.W. Feather          | If you lie to the compiler,
Email: clive at davros.org     | it will get its revenge.
Web: http://www.davros.org  |   - Henry Spencer
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