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.



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
-------

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. 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

A self-containted erlang solution would avoid these pitfalls, but to be fair, it introduces a few others:

 * you (the admin) are responsible for updating the timezone database yourself
 * ezic has not yet been battle tested

I think both of these issues will disappear over time, so I opted to write ezic.




License
-------

This project is in the public domain.