ezic
====
ezic is a set of erlang utilities for the Olsen timezone database files. See the [tz database](http://www.twinsun.com/tz/tz-link.htm) page for more information.



License
-------

This project is in the public domain.



Status
------

2010.11.04

 * ezic is "apparently functional". It has been tested very lightly, a bit by unit tests, but mostly by inspection. It's probably not fit for production use.


API
---

 * `ezic:localtime(TimeZone) -> datetime()`
 * `ezic:utc_to_time(universal_datetime(), TimeZone) -> local_datetime()`
 * `ezic:utc_from_time(local_datetime(), TimeZone) -> universal_datetime()`
 * `ezic:zone_convert(from_datetime(), TimeZoneFrom, TimeZoneTo) -> to_datetime()`



Admin API
-------

 * `ezic:load("/path/to/tzdata") -> ok`



Setup
-----
  
    # download the timezone data files
    wget 'ftp://elsie.nci.nih.gov/pub/tzdata*.tar.gz'
    tar -xvzf tzdata*.tar.gz -C /path/to/tzdata

    # remove a few troublesome files
    cd /path/to/tzdata
    rm *.sh *.tab factory
  
    # build and run ezic
    make all run
    1> ezic:load("/path/to/tzdata").
    2> ezic:localtime("Australia/Adelaide").




Purpose
-------

Erlang/OTP doesn't have a timezone library, so I decided to write one.

The [recommended way](http://www.erlang.org/pipermail/erlang-questions/2006-December/024291.html) of handling timezones in erlang involves setting the system environment variable `TZ` to the desired timezone, then calling erlang time functions. As far as I can tell, this technique has a few key issues:

 * it only works on *nix systems,
 * it depends on your system's timezone data (preventing custom timezone hackery), and
 * you can create race conditions if you aren't careful

ezic doesn't have these problems. ezic is, however, a young project with who-knows-how-many problems of its own ;)