Fwd: Re: system-config-date?

[Robert Moskowitz]

To the Xfce developers:

Over on the Fedora test list, we have been having a lively discussion 
about replacement for system-config-date.  Finally Adam Williamson of 
Fedoraproject contributed the following.

It would be great if Xfce could implement something along the lines that 
Adam says Gnome has done.

thanks


-------- Forwarded Message --------
Subject: 	Re: system-config-date?
Date: 	Fri, 24 Aug 2018 10:34:35 -0700
From: 	Adam Williamson <adamwill at fedoraproject.org>
Reply-To: 	For testing and quality assurance of Fedora releases 
<test at lists.fedoraproject.org>
Organization: 	Fedora Project
To: 	For testing and quality assurance of Fedora releases 
<test at lists.fedoraproject.org>, Jon Ingason <jon.ingason at telia.com>



On Fri, 2018-08-24 at 12:00 -0400, Robert Moskowitz wrote:
> 
> You have to know the format of the zoneinfo directory for this to work.  
> Like start with Am to get American cities.  Not start with H for 
> Helsinki; all you get is Hongkong and HST.
> 
> And you have to know a city in the list near where you are.  Many times 
> my city is not included.  Well we 'know' that San Diego and San 
> Francisco are in the same zone as Los_Angeles.  But this is all stuff 
> you have to figure out for yourself when the list comes up. s-c-d is 
> very good at showing you a city near where you are looking for...
> 
> Mostly it works.  There have been a few times I have been challenged and 
> had to look at my phone to confirm the timezone.  Just a few. ;)

The zoneinfo/tzdata database is not formatted for human use. The way it
was explained to me one time, the basic principle is that an entry is
added to it any time some kind of new timezone definition or DST
variation or something happens, associated with the largest or most
prominent city related to that event, and these entries are never
removed (so the database acts as a record of *historical* as well as
*current* timezone variations).

This is basically why it has such an apparently-quixotic set of cities
in it, and explains a lot of the "why X but not Y?" questions -
basically because X at *some* point did something which was not yet
recorded in the zoneinfo database, but Y never did.

IMBW, that's just my memory of how it was explained to me. But
basically, it's *not* a big list of Cities You Might Possibly Know
About and the timezones they're currently in, but it looks sufficiently
*like* one that GUI apps often just take its city list and let you
search it, or something like that.

AIUI again, the way GNOME does it better is using libgweather:

https://gitlab.gnome.org/GNOME/libgweather

which has a gigantic database mapping cities (and other 'locations',
like airports and stuff) to tzdata timezones. That's why you can look
up just about anywhere in GNOME and find the time there, or set your
time for that place:

https://gitlab.gnome.org/GNOME/libgweather/tree/master/data

I don't know how heavy libgweather's deps are, but it'd probably be a
good idea for KDE and Xfce to consider using it to do something similar
to GNOME, or perhaps for the data to be split out if libgweather's deps
are inappropriately heavy just for this purpose...
-- 
Adam Williamson
Fedora QA Community Monkey
IRC: adamw | Twitter: AdamW_Fedora | XMPP: adamw AT happyassassin . net
http://www.happyassassin.net
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