[tz] Missing entry for Heard Island and MacDonald Islands

Ian Abbott abbotti at mev.co.uk
Fri May 11 09:34:23 UTC 2012

On 2012-05-11 09:52, dfg dfg wrote:
> Hi everyone,
> I am a developer by trade, so I am not sure if I have stumbled onto some
> missing data in the tz database. I am accessing the database using PHP
> (www.php.net <http://www.php.net>) which uses the latest version of the
> tz database (2012.3). I can use one of the built in functions to lookup
> timezone information for a given country using its ISO 3166-1 two letter
> country code
> (http://www.php.net/manual/en/datetimezone.listidentifiers.php).
> I am currently building an application and found that Heard Island and
> MacDonald Islands (ISO code HM) does not exist in the database. After a
> quick look at the tz data, I was also not able to find anything about
> Heard Island and MacDonald Island in the files. I believe that there
> should be an entry for Heard Island and MacDonald Islands (HM) which
> uses the timezone Australia/Perth.
> Is it possible that the entry was intentionally excluded for some
> reason? Or was it just missing from the database?

The tz database doesn't provide a mapping from country codes to 
timezones, but it does map each time zone name to a single, 
representative geographical location (i.e. the city or settlement name 
used to construct the time zone name).  Other projects may provide 
mappings from any location on Earth (or at least the inhabited regions) 
to the appropriate entry in the tz database for that location.

If Heard Island and MacDonald Island have had wall-clock times different 
to Australia/Perth in the past (and especially since Jan 1, 1970 
onwards), then they should have their own entry in the tz database.

-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti at mev.co.uk>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-

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