Module description
==================
This module provides simple import and export functions for datetime strings
specified by RFC822, RFC2822 and the RSS specification to erlang datetime
tuples as returned for example by erlang:universaltime() or erlang:localtime().


datetime_encode
===============
Convert a erlang datetime struct to its string representation according to
either RFC822 or the RSS specification.

datetime_encode( DateTime, TimeZone, SpecType )
                    |         |         +------- Defaults to 'rfc2822'
                    |         +------- Defaults to 'GMT'
                    +------- Defaults to erlang:universaltime()

DateTime must be of the form {{Year,Month,Day},{Hour,Minute,Second}}. This
         form is returned for example by the erlang functions
         universaltime() or localtime().
TimeZone has to be a zone according to RFC822. Additional time zones may be
         accepted in the future.
SpecType can be either 'rfc822' or 'rss'. Both specifications are basically
         the same except for the length of the year. RSS supports both, two
         and four digit years while rfc882 only accepts two digit year
         representation.
			Some specifications of rfc2882 marked as obsolete and comments are not
			supported as they are basically never used in the real world.


datetime_decode
===============
Converts a DateTime string according to rfc822 or RSS specifications into an
erlang datetime tupel. The first parameter is the datetime string, the second
specifies the handling of years represented as two digits.
According to the RFC822 a year is only represented by its two last digits.
There are some methods provided for expanding those short year representations
to a full year. You can choose between the following expansion rules. The
default rule is 'smart'.
 smart             If the two digit year is less or equal of the two last
                   digits of the current year, assume that the date is from
                   the current century. Otherwise assume that the date is
                   from last century.
                   Example (Current year is 2012):
                     12  will become  2012
                     34  will become  1934
                     05  will become  2005
 current_century   It is assumed that all dates are from this century.
 no_alternation    No alternation is done. Thus two digit years stay as they
                   are.
 DIGIT             DIGIT may be any integer. Using this method you can
                   specify a concrete century. This number is basically
                   added to the two digit year. Thus 34 with DIGIT = 1800
                   will become 1834.