Removing locale timezone information

[Paul Eggert]

keld@keldix.com wrote:
> I thing tz data changes are not very frequent

No, they're reasonably common: about ten times a year.  For example, yesterday 
North Korea announced they're changing to +0830 on August 15 and we'll generate 
a new tzdata release before then.  We can't reasonably expect glibc releases 
that often or so quickly.

Quick turnaround is important here.  For example, between the time that a new 
tzdata release is announced, and the time my Ubuntu desktop is automatically 
updated with the new data, can be a matter of hours.  (I'm not doing anything 
special; I'm just an ordinary Ubuntu user in this regard.)  This is helpful 
becausee countries sometimes don't give us much notice.  Again, not something 
suited to glibc's schedule.

> are Olson tzdata used in GNU interfaces?

Yes, e.g., in strftime, localtime_r, and tzset.

 > Was there a differnce between German
 > an Swiss timezones? Something with Switzerland not being EU?

Yes, German and Swiss daylight-saving rules disagreed in 1980, and Büsingen 
(which is a German enclave surrounded by the Swiss canton Shaffhausen) used 
Swiss rules.

 > Both your examples are for countries with two timezones

Actually more than two, depending on which version of tzdata you're using. 
China has also had Asia/Chongqing, Asia/Harbin, and Asia/Kashgar in past 
versions.  It may well have more than two in the future.

 > I guess that one of them are the one that the majority will use.

True for China and Germany today, but not for the US, Canada, or Russia.  And in 
several other countries (Australia, Brazil, Indonesia, Mexico, ...) a 
significant minority of users won't want the majority's preference.  We're 
talking about a lot of users here, not just a few exceptional cases.