[tz] Converting cities to tz identifiers (tangent)

[Paul Eggert]

On 02/20/2018 09:46 AM, John Hawkinson wrote:
> in general, for most locations, the US/* ("backward") form seemed the better choice.

It depends on how portable you want to be. Some implementations do not 
use the 'backward' file, so TZ='US/Eastern' does not work for them. 
FreeBSD is one such, or at least it was the last time I recall checking; 
see Garrett Wollman's email 
<https://mm.icann.org/pipermail/tz/2008-May/014941.html>. So, in 
practice I would say TZ='America/New_York' is more portable than 
TZ='US/Eastern'.

If New York ever switches to Atlantic time (unlikely but conceivable 
given the current state of US politics), we'll link some other location 
to US/Eastern in the 'backward' file. Although it's not now clear what 
that other location would be (it'd depend on what part of the US 
switches), one candidate would be America/Indiana/Indianapolis. This is 
because if Jacksonville, Philadelphia and New York all switch to 
Atlantic time, then Indianapolis could well be the largest remaining 
city observing US Eastern time. This should amuse those of us who recall 
the history of UT offsets in Indiana.