[tz] Beginner's help request

Paul Eggert eggert at cs.ucla.edu
Mon Nov 20 18:43:40 UTC 2017

On 11/20/2017 04:54 AM, Daniel Ford wrote:
> So my question now is, how does one know which file to search for zone/rules
> for any given region/city from zone1970.tab?

As zefram mentioned, your best bet might be to look at tzdata.zi, which 
contains all the data for all the entries in zone1970.tab. You can get 
the current released version here:


This file contains only ASCII text; it is designed to be small and 
compressible. If your network client supports "Content-Encoding: gzip" 
(most do, these days), the payload is currently 25,895 bytes on the 
network and is 106,378 bytes uncompressed. This is small enough that it 
should not be an undue burden on the master iana.org servers if your 
small number of clocks periodically poll for updates in the usual way 
(they can first get the Last-Modified: header to see whether they're 

Doing it this way would relieve you of the burden of maintaining your 
own time servers, though of course your customers would then be at the 
mercy of the IANA, which has not yet committed to supporting this URL 
for the indefinite future. (Your call. :-)

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