[tz] Version in zoneinfo files?

[Guy Harris]

On Oct 26, 2015, at 2:50 PM, Bradley White <bww at acm.org> wrote:

> On Sun, Oct 25, 2015 at 2:30 PM, Guy Harris <guy at alum.mit.edu> wrote:
>> Is this just something to let people know whether they have an up-to-date version of the tzdb files or not?
> 
> Yes, although I think of it simply as let people know what version of a tzdb file they have.  (Whether that is the latest version is a separate question.)

Which version they have, or which version of the IANA tzdb the version they have is based on? :-)

> I would even propose an additional self-identification step: include the zone name in tzdb file.

Which zone name is "the" zone name?  The zone name on the system on which zic was run?

> Then you could tell, for example, where /etc/localtime came from.

Well, on my system, it came from a symlink() call:

$ ls -l /etc/localtime
lrwxr-xr-x  1 root  wheel  39 Oct 10 21:20 /etc/localtime -> /usr/share/zoneinfo/America/Los_Angeles

although if I were traveling there would be more than such symlink() call, one made whenever the machine changes what tzdb zone it's in (I checked "Set time zone automatically using current location" in the "Time Zone" subpane of the "Date & Time" pane of System Preferences").  Should the code making those symlink() calls also write to each compiled tzdb file under /usr/share/zoneinfo, updating the zone name?