[tz] Getting current tzdb version in use

Paul Eggert eggert at cs.ucla.edu
Fri Jul 20 18:35:59 UTC 2018

Robert Elz wrote:

> test for what you need to know - exactly - never simply
> assume that if X is detected, then (an unrelated) Y will also exist

This is good advice. It's a primary design philosophy of Autoconf: test for what 
you need, not for version numbers. Although you can't always do it, it's better 
to do it when you can.

> saving a few bytes of
> download time in an environment when half the world are streaming
> movies (or porn) and the rest are trying to download kde or openoffice
> just isn't an objective that matters.

Admittedly it's not a big deal, but if we're upgrading tzdata in 5 billion 
mobile devices ten times per year and saving 50 kB per upgrade, that's 250 TB of 
mobile data and Internet traffic saved worldwide per year. Although this is only 
a tiny fraction of total use (Cisco predicts 200 EB for such traffic in 2018), 
even a 1 part-per-million decrease would be a (tiny) win.

It'd be like Hogan's Heroes vs the German army; you get only small victories, 
but you do what you can and every bit helps.

My source for traffic estimates is the last page of:


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