** 什么是ISO 8601**

国际标准化组织的国际标准ISO 8601是日期和时间表示方法，全称为<<数据存储和交互形式 信息交换 日期和时间的表示方法>>。目前最新为第三版ISO8601:2004, 第一版为ISO8601:1988, 第二版为ISO8601:2000。

日期和时间的组合表示法：

合并表示时，要在时间前面加一大写字母T, 如要表示北京时间2004年5月3日下午5点30分8秒，可以写成2004-05-03T17:30:08+08:00或20040503T173008+08。

详细内容请查阅百度百科

或

erlang时间与日期处理

** iso8601库**

下面把德国时间转换为北京时间

世界各国时间转换网址：

使用iso8601库进行转换结果：

代码如下：

-module(iso8601).-export([add_time/4,         format/1,         parse/1,         parse_exact/1]).-export_types([timestamp/0]).-define(MIDNIGHT, {0,0,0}).-define(V, proplists:get_value).-type datetime_plist() :: list({atom(), integer()}).-type maybe(A) :: undefined | A.-type timestamp() :: {MegaSecs::integer(),                      Secs::integer(),                      MicroSecs::integer() | float()}.%% API-spec add_time (calendar:datetime(), integer(), integer(), integer())               -> calendar:datetime().%% @doc Add some time to the supplied `calendar:datetime()'.add_time(Datetime, H, M, S) ->    apply_offset(Datetime, H, M, S).-spec format (calendar:datetime() | timestamp()) -> binary().%% @doc Convert a `util:timestamp()' or a calendar-style `{date(), time()}'%% tuple to an ISO 8601 formatted string. Note that this function always%% returns a string with no offset (i.e., ending in "Z").format({_,_,_}=Timestamp) ->    format(calendar:now_to_datetime(Timestamp));format({
   {Y,Mo,D}, {H,Mn,S}}) when is_float(S) ->    FmtStr = "~4.10.0B-~2.10.0B-~2.10.0BT~2.10.0B:~2.10.0B:~9.6.0fZ",    IsoStr = io_lib:format(FmtStr, [Y, Mo, D, H, Mn, S]),    list_to_binary(IsoStr);format({
   {Y,Mo,D}, {H,Mn,S}}) ->    FmtStr = "~4.10.0B-~2.10.0B-~2.10.0BT~2.10.0B:~2.10.0B:~2.10.0BZ",    IsoStr = io_lib:format(FmtStr, [Y, Mo, D, H, Mn, S]),    list_to_binary(IsoStr).-spec parse (string()) -> calendar:datetime().%% @doc Convert an ISO 8601 formatted string to aparse(Bin) when is_binary(Bin) ->    parse(binary_to_list(Bin));parse(Str) ->    {
   {Date, {H, M, S}}, Subsecond} = year(Str, []),    {Date, {H, M, S + round(Subsecond)}}.-spec parse_exact (string()) -> calendar:datetime().%% @doc Convert an ISO 8601 formatted string to a `{date(), time()}'%% tuple with seconds precision to 3 decimal palcesparse_exact(Bin) when is_binary(Bin) ->    parse_exact(binary_to_list(Bin));parse_exact(Str) ->    {
   {Date, {H, M, S}}, SecondsDecimal} = year(Str, []),    {Date, {H, M, S + SecondsDecimal}}.%% Private functionsyear([Y1,Y2,Y3,Y4|Rest], Acc) ->    acc([Y1,Y2,Y3,Y4], Rest, year, Acc, fun month_or_week/2);year(_, _) ->    error(badarg).month_or_week([], Acc) ->    datetime(Acc);month_or_week([$-,$W,W1,W2|Rest], Acc) ->    acc([W1,W2], Rest, week, Acc, fun week_day/2);month_or_week([$-,D1,D2,D3], Acc) ->    %% ordinal date, no time    io:format("Ordinal date, no time!~n"),    acc_ordinal_date(D1, D2, D3, [], Acc, fun hour/2);month_or_week([$-,D1,D2,D3,$T|Rest], Acc) ->    %% ordinal date with time    io:format("Ordinal date, time is ~p!~n", [Rest]),    acc_ordinal_date(D1, D2, D3, [$T|Rest], Acc, fun hour/2);month_or_week([$-,M1,M2|Rest], Acc) ->    acc([M1,M2], Rest, month, Acc, fun month_day/2);month_or_week([$W,W1,W2|Rest], Acc) ->    acc([W1,W2], Rest, week, Acc, fun week_day_no_hyphen/2);month_or_week([M1,M2|Rest], Acc) ->    acc([M1,M2], Rest, month, Acc, fun month_day_no_hyphen/2);month_or_week(_, _) ->    error(badarg).week_day([], Acc) ->    datetime(Acc);week_day([$-,D|Rest], Acc) ->    acc([D], Rest, week_day, Acc, fun hour/2);week_day(_, _) ->    error(badarg).week_day_no_hyphen([], Acc) ->    datetime(Acc);week_day_no_hyphen([D|Rest], Acc) ->    acc([D], Rest, week_day, Acc, fun hour/2);week_day_no_hyphen(_, _) ->    error(badarg).month_day([], Acc) ->    datetime(Acc);month_day([$-,D1,D2|Rest], Acc) ->    acc([D1,D2], Rest, month_day, Acc, fun hour/2);month_day(_, _) ->    error(badarg).month_day_no_hyphen([], _) ->    error(badarg); % omission of day disallowed by spec in this casemonth_day_no_hyphen([D1,D2|Rest], Acc) ->    acc([D1,D2], Rest, month_day, Acc, fun hour/2);month_day_no_hyphen(_, _) ->    error(badarg).hour([], Acc) ->    datetime(Acc);hour([$T,H1,H2,$.|Rest], Acc) ->    acc([H1,H2], Rest, hour, Acc, fun hour_decimal/2);hour([$T,H1,H2,$,|Rest], Acc) ->    acc([H1,H2], Rest, hour, Acc, fun hour_decimal/2);hour([$T,H1,H2|Rest], Acc) ->    acc([H1,H2], Rest, hour, Acc, fun minute/2);hour(_, _) ->    error(badarg).hour_decimal(Str, Acc) ->    decimal(Str, Acc, hour_decimal).minute([], Acc) ->    datetime(Acc);minute([$:,M1,M2,$.|Rest], Acc) ->    acc([M1,M2], Rest, minute, Acc, fun minute_decimal/2);minute([$:,M1,M2,$,|Rest], Acc) ->    acc([M1,M2], Rest, minute, Acc, fun minute_decimal/2);minute([$:,M1,M2|Rest], Acc) ->    acc([M1,M2], Rest, minute, Acc, fun second/2);minute([M1,M2,$.|Rest], Acc) ->    acc([M1,M2], Rest, minute, Acc, fun minute_decimal/2);minute([M1,M2,$,|Rest], Acc) ->    acc([M1,M2], Rest, minute, Acc, fun minute_decimal/2);minute([M1,M2|Rest], Acc) ->    acc([M1,M2], Rest, minute, Acc, fun second_no_colon/2);minute(_, _) ->    error(badarg).minute_decimal(Str, Acc) ->    decimal(Str, Acc, minute_decimal).second([], Acc) ->    datetime(Acc);second([$:,S1,S2,$.|Rest], Acc) ->    acc([S1,S2], Rest, second, Acc, fun second_decimal/2);second([$:,S1,S2,$,|Rest], Acc) ->    acc([S1,S2], Rest, second, Acc, fun second_decimal/2);second([$:,S1,S2|Rest], Acc) ->    acc([S1,S2], Rest, second, Acc, fun offset_hour/2);second(_, _) ->    error(badarg).second_no_colon([], Acc) ->    datetime(Acc);second_no_colon([S1,S2,$.|Rest], Acc) ->    acc([S1,S2], Rest, second, Acc, fun second_decimal/2);second_no_colon([S1,S2,$,|Rest], Acc) ->    acc([S1,S2], Rest, second, Acc, fun second_decimal/2);second_no_colon([S1,S2|Rest], Acc) ->    acc([S1,S2], Rest, second, Acc, fun offset_hour/2);second_no_colon(_, _) ->    error(badarg).second_decimal(Str, Acc) ->    decimal(Str, Acc, second_decimal).decimal([], _, _) ->    error(badarg);decimal(Str, Acc, Key) ->    F = fun(X) when is_integer(X), X >= $0, X =< $9 ->                true;           (_) ->                false        end,    {Parts, Rest} = lists:splitwith(F, Str),    acc_float([$0,$.|Parts], Rest, Key, Acc, fun offset_hour/2).offset_hour([], Acc) ->    datetime(Acc);offset_hour([$Z], Acc) ->    datetime(Acc);offset_hour([$+,H1,H2|Rest], Acc) ->    acc([H1,H2], Rest, offset_hour, Acc, fun offset_minute/2);offset_hour([$-,H1,H2|Rest], Acc) ->    acc([H1,H2], Rest, offset_hour, [{offset_sign, -1}|Acc], fun offset_minute/2);offset_hour(_, _) ->    error(badarg).offset_minute([], Acc) ->    datetime(Acc);offset_minute([$:,M1,M2], Acc) ->    acc([M1,M2], [], offset_minute, Acc, fun datetime/2);offset_minute([M1,M2], Acc) ->    acc([M1,M2], [], offset_minute, Acc, fun datetime/2);offset_minute(_, _) ->    error(badarg).acc(IntStr, Rest, Key, Acc, NextF) ->    Acc1 = [{Key, list_to_integer(IntStr)}|Acc],    NextF(Rest, Acc1).acc_float(FloatStr, Rest, Key, Acc, NextF) ->    Acc1 = [{Key, list_to_float(FloatStr)}|Acc],    NextF(Rest, Acc1).acc_ordinal_date(D1, D2, D3, Rest, Acc, NextF) ->    Days = list_to_integer([D1, D2, D3]),    Days > 0 orelse error(badarg),    Year = ?V(year, Acc),    Year =/= undefined orelse error(badarg),    DaysInMonths = days_in_months_for_year(Year),    { Month, Day } = unpack_ordinal_date(Days, DaysInMonths),    Acc1 = [{ month, Month }, { month_day, Day }|Acc],    NextF(Rest, Acc1).unpack_ordinal_date(Days, DaysInMonths) -> unpack_ordinal_date(1, Days, DaysInMonths).unpack_ordinal_date(_Month, _Days, []) -> error(badarg), { 0, 0 };unpack_ordinal_date(_Month, Days, _DaysInMonths) when Days < 0 -> error(badarg), { 0, 0 };unpack_ordinal_date(Month, Days, [DaysThisMonth|DaysInMonths]) ->    case Days > DaysThisMonth of        true -> unpack_ordinal_date(Month + 1, Days - DaysThisMonth, DaysInMonths);        _ -> { Month, Days }    end.days_in_months_for_year(Year) ->    case is_leap_year(Year) of        true -> [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];        false -> [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]    end.is_leap_year(Year) ->    case Year rem 100 of         0 -> Year rem 400 =:= 0;         _ ->  Year rem 4 =:= 0    end.add_decimal(Datetime, Plist) ->    HDecimal = ?V(hour_decimal, Plist, 0.0),    MDecimal = ?V(minute_decimal, Plist, 0.0),    apply_offset(Datetime, HDecimal, MDecimal, 0.0).datetime(Plist) ->    {Date, WeekOffsetH} = make_date(Plist),    Time = {?V(hour, Plist, 0), ?V(minute, Plist, 0), ?V(second, Plist, 0)},    Datetime = add_decimal({Date, Time}, Plist),    OffsetSign = ?V(offset_sign, Plist, 1),    OffsetH = -1 * OffsetSign * ?V(offset_hour, Plist, 0),    OffsetM = -1 * OffsetSign * ?V(offset_minute, Plist, 0),    { apply_offset(Datetime, WeekOffsetH+OffsetH, OffsetM, 0), ?V(second_decimal, Plist, 0.0) }.datetime(_, Plist) ->    datetime(Plist).-spec make_date (datetime_plist())                -> {Date::calendar:date(), WeekOffsetH::non_neg_integer()}.%% @doc Return a `tuple' containing a date and, if the date is in week format,%% an offset in hours that can be applied to the date to adjust it to midnight%% of the day specified. If month format is used, the offset will be zero.make_date(Plist) ->    Year = ?V(year, Plist),    Year =/= undefined orelse error(badarg),    make_date(Year, ?V(month, Plist, 1), ?V(week, Plist), Plist).-spec make_date (non_neg_integer(),                 maybe(pos_integer()),                 maybe(pos_integer()),                 datetime_plist())                -> {calendar:date(), non_neg_integer()}.%% @doc Return a `tuple' containing a date and - if the date is in week format%% (i.e., `Month' is undefined, `Week' is not) - an offset in hours that can be%% applied to the date to adjust it to midnight of the day specified. If month%% format is used (i.e., `Week' is undefined, `Month' is not), the offset will%% be zero.make_date(Year, Month, undefined, Plist) ->    Date = {Year, Month, ?V(month_day, Plist, 1)},    {Date, 0};make_date(Year, _, Week, Plist) ->    Weekday = ?V(week_day, Plist, 1),    OffsetH = ((Week-1)*7 + (Weekday-1))*24, % week/weekday offset in hours    {date_at_w01_1(Year), OffsetH}.-spec date_at_w01_1(pos_integer()) -> calendar:date().%% @doc Calculate the `calendar:date()' at ISO week 1, day 1 in the supplied%% year.date_at_w01_1(Year) ->    case calendar:day_of_the_week({Year,1,1}) of        1 -> {Year, 1, 1};        2 -> {Year-1, 12, 31};        3 -> {Year-1, 12, 30};        4 -> {Year-1, 12, 29};        5 -> {Year, 1, 4};        6 -> {Year, 1, 3};        7 -> {Year, 1, 2}    end.-spec apply_offset (calendar:datetime(), number(), number(), number())                   -> calendar:datetime().%% @doc Add the specified number of hours, minutes and seconds to `Datetime'.apply_offset(Datetime, H, M, S) ->    OffsetS = S + (60 * (M + (60 * H))),    Gs = round(OffsetS) + calendar:datetime_to_gregorian_seconds(Datetime),    calendar:gregorian_seconds_to_datetime(Gs).