ISO8601 to unix timestamp

gistfile1.erl

-module(iso8601_to_unixtimestamp).
-define(GREGORIAN_SECONDS_TO_UNIXTIMESTAMP_DIFFERENCE, 719528*24*3600).

-export([doit/0]).

parse_iso8601(DateString) ->
    {ok,[Year, Month, Day, Hour, Min, Sec],_} = io_lib:fread("~d-~d-~dT~d:~d:~dZ", DateString),
    {{Year,Month,Day},{Hour,Min,Sec}}.

ymdhms_to_gregorian_seconds({{Year,Month,Day},{Hour,Min,Sec}}) ->
    calendar:datetime_to_gregorian_seconds({{Year,Month,Day},{Hour,Min,Sec}}).

gregorian_seconds_to_unixtimestamp(Seconds) ->
    Seconds - ?GREGORIAN_SECONDS_TO_UNIXTIMESTAMP_DIFFERENCE.

convert_unixtimestamp_to_timestamp(UnixTimestamp) ->
    {UnixTimestamp div 1000000000000,
        UnixTimestamp div 1000000 rem 1000000,
        UnixTimestamp rem 1000000}.

timestamp_to_unixtimestamp({MegaSecs, Secs, MicroSecs}) ->
    MegaSecs * 1000000 * 1000000 + Secs * 1000000 + MicroSecs.


doit() ->
    ISO8601 = "2012-11-21T09:00:00Z",
    io:fwrite("ISO8601: ~s~n", [ISO8601]),

    DateTime = parse_iso8601(ISO8601),
    io:fwrite("DateTime: ~p~n", [DateTime]),

    GregorianSeconds = ymdhms_to_gregorian_seconds(DateTime),
    io:fwrite("GregorianSeconds: ~p~n", [GregorianSeconds]),

    UnixTimestamp = gregorian_seconds_to_unixtimestamp(GregorianSeconds),
    io:fwrite("UnixTimestamp: ~p~n", [UnixTimestamp]),

    Timestamp = convert_unixtimestamp_to_timestamp(UnixTimestamp),
    io:fwrite("Timestamp: ~p~n", [Timestamp]),

    UnixTimestamp2 = timestamp_to_unixtimestamp(Timestamp),
    io:fwrite("UnixTimestamp2: ~p~n", [UnixTimestamp2]),

    UnixTimestamp =:= UnixTimestamp2.

1> iso8601_to_unixtimestamp:doit().
ISO8601: 2012-11-21T09:00:00Z
DateTime: {{2012,11,21},{9,0,0}}
GregorianSeconds: 63520707600
UnixTimestamp: 1353488400
Timestamp: {0,1353,488400}
UnixTimestamp2: 1353488400
true
2>