Format logger timestamps according to RFC3339

6 files changed, 243 insertions, 104 deletions

diff --git a/lib/kernel/doc/src/logger_formatter.xml b/lib/kernel/doc/src/logger_formatter.xml
index 5f13e54365..370d61d338 100644
--- a/lib/kernel/doc/src/logger_formatter.xml
+++ b/lib/kernel/doc/src/logger_formatter.xml
@@ -155,11 +155,40 @@
 	  and <c>single_line</c>. See <seealso marker="#default_templates">Default
 	  Templates</seealso> for more information</p>
       </item>
-      <tag><c>utc = boolean()</c></tag>
+      <tag><c>time_designator = byte()</c></tag>
       <item>
-	<p>If set to <c>true</c>, all dates are displayed in Universal
-	  Coordinated Time.</p>
-	<p>Default is <c>false</c>.</p>
+	<p>Timestamps are formatted according to RFC3339, and the time
+	  designator is the character used as date and time
+	  separator.</p>
+	<p>Default is <c>$T</c>.</p>
+	<p>The value of this parameter is used as
+	  the <c>time_designator</c> option
+	  to <seealso marker="stdlib:calendar#system_time_to_rfc3339-2">
+	    <c>calendar:system_time_to_rcf3339/2</c></seealso>.</p>
+      </item>
+      <tag><c>time_offset = integer() | [byte()]</c></tag>
+      <item>
+	<p>The time offset, either a string or an integer, to be
+	  used when formatting the timestamp.</p>
+	<p>An empty string is interpreted as local time. The
+	  values <c>"Z"</c>, <c>"z"</c> or <c>0</c> are interpreted as
+	  Universal Coordinated Time (UTC).</p>
+	<p>Strings, other than <c>"Z"</c>, <c>"z"</c>, or <c>""</c>,
+	  must be on the form <c>±[hh]:[mm]</c>, for
+	  example <c>"-02:00"</c> or <c>"+00:00"</c>.</p>
+	<p>Integers must be in microseconds, meaning that the
+	  offset <c>7200000000</c> is equivalent
+	  to <c>"+02:00"</c>.</p>
+	<p>The default value is an empty string, meaning that
+	  timestamps are displayed in local time. However, for
+	  backwards compatibility, if the SASL environment
+	  variable <seealso marker="sasl:sasl_app#utc_log">
+	    <c>utc_log</c></seealso><c>=true</c>, the default is
+	  changed to <c>"Z"</c>, meaning that timestamps are displayed
+	  in UTC.</p>
+	<p>The value of this parameter is used as the <c>offset</c>
+	  option to <seealso marker="stdlib:calendar#system_time_to_rfc3339-2">
+	    <c>calendar:system_time_to_rcf3339/2</c></seealso>.</p>
       </item>
     </taglist>
   </section>
@@ -174,7 +203,7 @@
 
     <p>The log event used in the examples is:</p>
     <code>
-?LOG_ERROR("name: ~p~nexit_reason: ~p",[my_reg_name,"It crashed"])</code>
+?LOG_ERROR("name: ~p~nexit_reason: ~p",[my_name,"It crashed"])</code>
 
     <taglist>
       <tag><c>legacy_header=true</c></tag>
@@ -182,9 +211,9 @@
 	<p>Default template: <c>[{logger_formatter,header},"\n",msg,"\n"]</c></p>
 
 	<p>Example log entry:</p>
-	<code>
-=ERROR REPORT==== 29-Dec-2017::13:30:51.245123 ===
-name: my_reg_name
+	<code type="none">
+2018-05-16T11:55:50.448382+02:00 error:
+name: my_name
 exit_reason: "It crashed"</code>
 
 	<p>Notice that all eight levels might occur in the heading,
@@ -198,7 +227,7 @@ exit_reason: "It crashed"</code>
 	<p>Default template: <c>[time," ",level,": ",msg,"\n"]</c></p>
 
 	<p>Example log entry:</p>
-	<code>2017-12-29 13:31:49.640317 error: name: my_reg_name, exit_reason: "It crashed"</code>
+	<code type="none">2018-05-16T11:55:50.448382+02:00 error: name: my_name, exit_reason: "It crashed"</code>
       </item>
 
       <tag><c>legacy_header=false, single_line=false</c></tag>
@@ -206,9 +235,9 @@ exit_reason: "It crashed"</code>
 	<p>Default template: <c>[time," ",level,":\n",msg,"\n"]</c></p>
 
 	<p>Example log entry:</p>
-	<code>
-2017-12-29 13:32:25.191925 error:
-name: my_reg_name
+	<code type="none">
+2018-05-16T11:55:50.448382+02:00 error:
+name: my_name
 exit_reason: "It crashed"</code>
       </item>
     </taglist>
diff --git a/lib/kernel/src/logger_formatter.erl b/lib/kernel/src/logger_formatter.erl
index 0d55244034..602c666cc7 100644
--- a/lib/kernel/src/logger_formatter.erl
+++ b/lib/kernel/src/logger_formatter.erl
@@ -39,7 +39,8 @@
                   max_size=>pos_integer() | unlimited,
                   depth=>pos_integer() | unlimited,
                   template=>template(),
-                  utc=>boolean()}.
+                  time_designator=>byte(),
+                  time_offset=>integer()|[byte()]}.
 format(#{level:=Level,msg:=Msg0,meta:=Meta},Config0)
   when is_map(Config0) ->
     Config = add_default_config(Config0),
@@ -196,16 +197,12 @@ truncate(String,Size) ->
             String
     end.
 
-format_time(Timestamp,Config) when is_integer(Timestamp) ->
-    {Date,Time,Micro} = timestamp_to_datetimemicro(Timestamp,Config),
-    format_time(Date,Time,Micro);
-format_time(Other,_Config) ->
-    %% E.g. a string
-    to_string(Other).
-
-format_time({Y,M,D},{H,Min,S},Micro) ->
-    io_lib:format("~4w-~2..0w-~2..0w ~2w:~2..0w:~2..0w.~6..0w",
-                  [Y,M,D,H,Min,S,Micro]).
+format_time(Timestamp,#{time_offset:=Offset,time_designator:=Des})
+  when is_integer(Timestamp) ->
+    SysTime = Timestamp + erlang:time_offset(microsecond),
+    calendar:system_time_to_rfc3339(SysTime,[{unit,microsecond},
+                                             {offset,Offset},
+                                             {time_designator,Des}]).
 
 %% Assuming this is monotonic time in microseconds
 timestamp_to_datetimemicro(Timestamp,Config) when is_integer(Timestamp) ->
@@ -213,12 +210,12 @@ timestamp_to_datetimemicro(Timestamp,Config) when is_integer(Timestamp) ->
     Micro = SysTime rem 1000000,
     Sec = SysTime div 1000000,
     UniversalTime =  erlang:posixtime_to_universaltime(Sec),
-    {Date,Time} =
-        case Config of
-            #{utc:=true} -> UniversalTime;
-            _ -> erlang:universaltime_to_localtime(UniversalTime)
+    {{Date,Time},UtcStr} =
+        case offset_to_utc(maps:get(time_offset,Config)) of
+            true -> {UniversalTime,"UTC "};
+            _ -> {erlang:universaltime_to_localtime(UniversalTime),""}
         end,
-    {Date,Time,Micro}.
+    {Date,Time,Micro,UtcStr}.
 
 format_mfa({M,F,A}) when is_atom(M), is_atom(F), is_integer(A) ->
     atom_to_list(M)++":"++atom_to_list(F)++"/"++integer_to_list(A);
@@ -231,9 +228,11 @@ maybe_add_legacy_header(Level,
                         #{time:=Timestamp}=Meta,
                         #{legacy_header:=true}=Config) ->
     #{title:=Title}=MyMeta = add_legacy_title(Level,maps:get(?MODULE,Meta,#{})),
-    {{Y,Mo,D},{H,Mi,S},Micro} = timestamp_to_datetimemicro(Timestamp,Config),
-    Header = io_lib:format("=~ts==== ~w-~s-~4w::~2..0w:~2..0w:~2..0w.~6..0w ~s===",
-                           [Title,D,month(Mo),Y,H,Mi,S,Micro,utcstr(Config)]),
+    {{Y,Mo,D},{H,Mi,S},Micro,UtcStr} =
+        timestamp_to_datetimemicro(Timestamp,Config),
+    Header =
+        io_lib:format("=~ts==== ~w-~s-~4w::~2..0w:~2..0w:~2..0w.~6..0w ~s===",
+                      [Title,D,month(Mo),Y,H,Mi,S,Micro,UtcStr]),
     Meta#{?MODULE=>MyMeta#{header=>Header}};
 maybe_add_legacy_header(_,Meta,_) ->
     Meta.
@@ -257,20 +256,20 @@ month(10) -> "Oct";
 month(11) -> "Nov";
 month(12) -> "Dec".
 
-utcstr(#{utc:=true}) -> "UTC ";
-utcstr(_) -> "".
-
+%% Ensure that all valid configuration parameters exist in the final
+%% configuration map
 add_default_config(Config0) ->
     Default =
         #{legacy_header=>false,
           single_line=>true,
-          chars_limit=>unlimited},
-    MaxSize = get_max_size(maps:get(max_size,Config0,false)),
-    Depth = get_depth(maps:get(depth,Config0,false)),
-    Utc = get_utc(maps:get(utc,Config0,false)),
+          chars_limit=>unlimited,
+          time_designator=>$T},
+    MaxSize = get_max_size(maps:get(max_size,Config0,undefined)),
+    Depth = get_depth(maps:get(depth,Config0,undefined)),
+    Offset = get_offset(maps:get(time_offset,Config0,undefined)),
     add_default_template(maps:merge(Default,Config0#{max_size=>MaxSize,
                                                      depth=>Depth,
-                                                     utc=>Utc})).
+                                                     time_offset=>Offset})).
 
 add_default_template(#{template:=_}=Config) ->
     Config;
@@ -284,33 +283,50 @@ default_template(#{single_line:=true}) ->
 default_template(_) ->
     ?DEFAULT_FORMAT_TEMPLATE.
 
-get_max_size(false) ->
+get_max_size(undefined) ->
     unlimited;
 get_max_size(S) ->
     max(10,S).
 
-get_depth(false) ->
+get_depth(undefined) ->
     error_logger:get_format_depth();
 get_depth(S) ->
     max(5,S).
 
-get_utc(false) ->
-    get_utc_config();
-get_utc(U) ->
-    U.
+get_offset(undefined) ->
+    utc_to_offset(get_utc_config());
+get_offset(Offset) ->
+    Offset.
+
+utc_to_offset(true) ->
+    "Z";
+utc_to_offset(false) ->
+    "".
 
 get_utc_config() ->
     %% SASL utc_log overrides stdlib config - in order to have uniform
     %% timestamps in log messages
     case application:get_env(sasl, utc_log) of
-        {ok, Val} -> Val;
-        undefined ->
+        {ok, Val} when is_boolean(Val) -> Val;
+        _ ->
             case application:get_env(stdlib, utc_log) of
-                {ok, Val} -> Val;
-                undefined -> false
+                {ok, Val} when is_boolean(Val) -> Val;
+                _ -> false
             end
     end.
 
+offset_to_utc(Z) when Z=:=0; Z=:="z"; Z=:="Z" ->
+    true;
+offset_to_utc([$+|Tz]) ->
+    case io_lib:fread("~d:~d", Tz) of
+        {ok, [0, 0], []} ->
+            true;
+        _ ->
+            false
+    end;
+offset_to_utc(_) ->
+    false.
+
 check_config(Config) when is_map(Config) ->
     do_check_config(maps:to_list(Config));
 check_config(Config) ->
@@ -341,8 +357,20 @@ do_check_config([{template,T}|Config]) when is_list(T) ->
         false ->
             {error,{invalid_formatter_template,?MODULE,T}}
     end;
-do_check_config([{utc,Utc}|Config]) when is_boolean(Utc) ->
-    do_check_config(Config);
+do_check_config([{time_offset,Offset}|Config]) ->
+    case check_offset(Offset) of
+        ok ->
+            do_check_config(Config);
+        error ->
+            {error,{invalid_formatter_config,?MODULE,{time_offset,Offset}}}
+    end;
+do_check_config([{time_designator,Char}|Config]) when Char>=0, Char=<255 ->
+    case io_lib:printable_latin1_list([Char]) of
+        true ->
+            do_check_config(Config);
+        false ->
+            {error,{invalid_formatter_config,?MODULE,{time_designator,Char}}}
+    end;
 do_check_config([C|_]) ->
     {error,{invalid_formatter_config,?MODULE,C}};
 do_check_config([]) ->
@@ -354,3 +382,22 @@ check_limit(unlimited) ->
     ok;
 check_limit(_) ->
     error.
+
+check_offset(I) when is_integer(I) ->
+    ok;
+check_offset(Tz) when Tz=:=""; Tz=:="Z"; Tz=:="z" ->
+    ok;
+check_offset([Sign|Tz]) when Sign=:=$+; Sign=:=$- ->
+    check_timezone(Tz);
+check_offset(_) ->
+    error.
+
+check_timezone(Tz) ->
+    try io_lib:fread("~d:~d", Tz) of
+        {ok, [_, _], []} ->
+            ok;
+        _ ->
+            error
+    catch _:_ ->
+            error
+    end.
diff --git a/lib/kernel/test/error_logger_warn_SUITE.erl b/lib/kernel/test/error_logger_warn_SUITE.erl
index a8087e11f9..ef55a2d339 100644
--- a/lib/kernel/test/error_logger_warn_SUITE.erl
+++ b/lib/kernel/test/error_logger_warn_SUITE.erl
@@ -480,9 +480,12 @@ rb_utc() ->
     UtcLog=case application:get_env(sasl,utc_log) of
                {ok,true} ->
                    true;
-               _AllOthers ->
+               {ok,false} ->
                    application:set_env(sasl,utc_log,true),
-                   false
+                   false;
+               undefined ->
+                   application:set_env(sasl,utc_log,true),
+                   undefined
            end,
     application:start(sasl),
     rb:start([{report_dir, rd()}]),
@@ -494,7 +497,12 @@ rb_utc() ->
     Sum=one_rb_findstr([],"UTC"),
     rb:stop(),
     application:stop(sasl),
-    application:set_env(sasl,utc_log,UtcLog),
+    case UtcLog of
+        undefined ->
+            application:unset_env(sasl,utc_log);
+        _ ->
+            application:set_env(sasl,utc_log,UtcLog)
+    end,
     stop_node(Node),
     ok.
     
diff --git a/lib/kernel/test/logger_SUITE.erl b/lib/kernel/test/logger_SUITE.erl
index 64968cbca2..e602fa2576 100644
--- a/lib/kernel/test/logger_SUITE.erl
+++ b/lib/kernel/test/logger_SUITE.erl
@@ -580,11 +580,6 @@ config_sanity_check(_Config) ->
                                                  #{report_cb=>fun(R) ->
                                                                       {"~p",[R]}
                                                               end}}),
-    {error,{invalid_formatter_config,logger_formatter,{utc,bad}}} =
-        logger:set_handler_config(h1,formatter,{logger_formatter,
-                                                #{utc=>bad}}),
-    ok = logger:set_handler_config(h1,formatter,{logger_formatter,
-                                                 #{utc=>true}}),
     {error,{invalid_formatter_config,logger_formatter,{chars_limit,bad}}} =
         logger:set_handler_config(h1,formatter,{logger_formatter,
                                                 #{chars_limit=>bad}}),
@@ -610,6 +605,42 @@ config_sanity_check(_Config) ->
     {error,{callback_crashed,{error,{badmatch,3},[{?MODULE,check_config,1,_}]}}} =
         logger:set_handler_config(h1,formatter,{?MODULE,crash}),
     ok = logger:set_handler_config(h1,custom,custom),
+
+    %% Old utc parameter is no longer allowed (replaced by time_offset)
+    {error,{invalid_formatter_config,logger_formatter,{utc,true}}} =
+         logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                 #{utc=>true}}),
+    {error,{invalid_formatter_config,logger_formatter,{time_offset,bad}}} =
+        logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                #{time_offset=>bad}}),
+    ok = logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                 #{time_offset=>0}}),
+    ok = logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                 #{time_offset=>""}}),
+    ok = logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                 #{time_offset=>"Z"}}),
+    ok = logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                 #{time_offset=>"z"}}),
+    ok = logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                 #{time_offset=>"-0:0"}}),
+    ok = logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                 #{time_offset=>"+10:13"}}),
+
+    {error,{invalid_formatter_config,logger_formatter,{time_offset,"+0"}}} =
+        logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                #{time_offset=>"+0"}}),
+
+    {error,{invalid_formatter_config,logger_formatter,{time_designator,bad}}} =
+        logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                #{time_designator=>bad}}),
+    {error,{invalid_formatter_config,logger_formatter,{time_designator,"s"}}} =
+        logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                #{time_designator=>"s"}}),
+    {error,{invalid_formatter_config,logger_formatter,{time_designator,0}}} =
+        logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                #{time_designator=>0}}),
+    ok = logger:set_handler_config(h1,formatter,{logger_formatter,
+                                                 #{time_designator=>$\s}}),
     ok.
 
 config_sanity_check(cleanup,_Config) ->
diff --git a/lib/kernel/test/logger_formatter_SUITE.erl b/lib/kernel/test/logger_formatter_SUITE.erl
index bd5bc2d2e4..9baadfd65a 100644
--- a/lib/kernel/test/logger_formatter_SUITE.erl
+++ b/lib/kernel/test/logger_formatter_SUITE.erl
@@ -73,7 +73,7 @@ all() ->
 default(_Config) ->
     String1 = format(info,{"~p",[term]},#{},#{}),
     ct:log(String1),
-    [_Date,_Time,"info:","term\n"] = string:lexemes(String1," "),
+    [_DateTime,"info:","term\n"] = string:lexemes(String1," "),
 
     Time = timestamp(),
     ExpectedTimestamp = default_time_format(Time),
@@ -364,7 +364,7 @@ chars_limit(_Config) ->
                  lists:seq(1,100),
                  maps:from_list(lists:zip(lists:seq(1,100),
                                           lists:duplicate(100,value)))]},
-    Meta = #{time=>"2018-04-26  9:15:40.449879"},
+    Meta = #{time=>timestamp()},
     Template = [time," - ", msg, "\n"],
     FC = #{template=>Template,
            depth=>unlimited,
@@ -376,7 +376,7 @@ chars_limit(_Config) ->
     L1 = string:length(String1),
     ct:log("String1: ~p~nLength1: ~p~n",[lists:flatten(String1),L1]),
     true = L1 > CL1,
-    true = L1 < CL1 + 10,
+    true = L1 < CL1 + 15,
 
     String2 = format(info,FA,Meta,FC#{chars_limit=>CL1,depth=>10}),
     L2 = string:length(String2),
@@ -388,13 +388,13 @@ chars_limit(_Config) ->
     L3 = string:length(String3),
     ct:log("String3: ~p~nLength3: ~p~n",[lists:flatten(String3),L3]),
     true = L3 > CL3,
-    true = L3 < CL3 + 10,
+    true = L3 < CL3 + 15,
 
     String4 = format(info,FA,Meta,FC#{chars_limit=>CL3,depth=>10}),
     L4 = string:length(String4),
     ct:log("String4: ~p~nLength4: ~p~n",[lists:flatten(String4),L4]),
     true = L4 > CL3,
-    true = L4 < CL3 + 10,
+    true = L4 < CL3 + 15,
 
     %% Test that max_size truncates the string which is limited by
     %% depth and chars_limit
@@ -433,29 +433,58 @@ format_mfa(_Config) ->
     ok.
     
 format_time(_Config) ->
-    Time1 = timestamp(),
-    ExpectedTimestamp1 = default_time_format(Time1),
-    String1 = format(info,{"~p",[term]},#{time=>Time1},#{}),
-    ct:log(String1),
-    " info: term\n" = string:prefix(String1,ExpectedTimestamp1),
-
-    Time2 = timestamp(),
-    ExpectedTimestamp2 = default_time_format(Time2,true),
-    String2 = format(info,{"~p",[term]},#{time=>Time2},#{utc=>true}),
-    ct:log(String2),
-    " info: term\n" = string:prefix(String2,ExpectedTimestamp2),
-
-    %% application:set_env(kernel,logger_utc,true),
-    %% Time3 = timestamp(),
-    %% ExpectedTimestamp3 = default_time_format(Time3,true),
-    %% String3 = format(info,{"~p",[term]},#{time=>Time3},#{}),
-    %% ct:log(String3),
-    %% " info: term\n" = string:prefix(String3,ExpectedTimestamp3),
+    Time = timestamp(),
+    Meta = #{time=>Time},
+    FC = #{template=>[time]},
+    Msg = {string,""},
+    ExpectedLocal = default_time_format(Time,false),
+    ExpectedUtc = default_time_format(Time,true),
+
+    %% default - local time
+    ExpectedLocal = format(info,Msg,Meta,FC),
+
+    %% time_offset config parameter to formatter
+    ExpectedLocal = format(info,Msg,Meta,FC#{time_offset=>""}),
+    ExpectedUtc = format(info,Msg,Meta,FC#{time_offset=>"Z"}),
+
+    %% stdlib utc_log works when time_offset parameter is not set
+    application:set_env(stdlib,utc_log,true),
+    ExpectedUtc = format(info,Msg,Meta,FC),
+
+    %% sasl utc_log overwrites stdlib utc_log
+    application:set_env(sasl,utc_log,false),
+    ExpectedLocal = format(info,Msg,Meta,FC),
+
+    %% sasl utc_log overwrites stdlib utc_log
+    application:set_env(sasl,utc_log,true),
+    application:set_env(stdlib,utc_log,false),
+    ExpectedUtc = format(info,Msg,Meta,FC),
+
+    %% time_offset config parameter to formatter
+    %% overwrites sasl and stdlib utc_log
+    application:set_env(sasl,utc_log,false),
+    ExpectedUtc = format(info,Msg,Meta,FC#{time_offset=>"Z"}),
+
+    %% time_offset config parameter to formatter
+    %% overwrites sasl and stdlib utc_log
+    application:set_env(sasl,utc_log,true),
+    application:set_env(stdlib,utc_log,true),
+    ExpectedLocal = format(info,Msg,Meta,FC#{time_offset=>""}),
+
+    %% time_designator config parameter to formatter
+    ExpectedLocalS = default_time_format(Time,false,$\s),
+    ExpectedUtcS = default_time_format(Time,true,$\s),
+
+    ExpectedLocalS = format(info,Msg,Meta,FC#{time_offset=>"",
+                                              time_designator=>$\s}),
+    ExpectedUtcS = format(info,Msg,Meta,FC#{time_offset=>"Z",
+                                            time_designator=>$\s}),
 
     ok.
 
 format_time(cleanup,_Config) ->
-    application:unset_env(kernel,logger_utc),
+    application:unset_env(sasl,utc_log),
+    application:unset_env(stdlib,utc_log),
     ok.
 
 level_or_msg_in_meta(_Config) ->
@@ -514,22 +543,17 @@ format(Log,Config) ->
 default_time_format(Timestamp) ->
     default_time_format(Timestamp,false).
 
-default_time_format(Timestamp0,Utc) when is_integer(Timestamp0) ->
+default_time_format(Timestamp,Utc) ->
+    default_time_format(Timestamp,Utc,$T).
+
+default_time_format(Timestamp0,Utc,Sep) ->
     Timestamp=Timestamp0+erlang:time_offset(microsecond),
-    %% calendar:system_time_to_rfc3339(Time,[{unit,microsecond}]).
-    Micro = Timestamp rem 1000000,
-    Sec = Timestamp div 1000000,
-    UniversalTime =  erlang:posixtime_to_universaltime(Sec),
-    {Date,Time} =
-        if Utc -> UniversalTime;
-           true -> erlang:universaltime_to_localtime(UniversalTime)
-        end,
-    default_time_format(Date,Time,Micro).
-
-default_time_format({Y,M,D},{H,Min,S},Micro) ->
-    lists:flatten(
-      io_lib:format("~4w-~2..0w-~2..0w ~2w:~2..0w:~2..0w.~6..0w",
-                    [Y,M,D,H,Min,S,Micro])).
+    Offset = if Utc -> "Z";
+                true -> ""
+             end,
+    calendar:system_time_to_rfc3339(Timestamp,[{unit,microsecond},
+                                               {time_designator,Sep},
+                                               {offset,Offset}]).
 
 integer(Str) ->
     is_integer(list_to_integer(Str)).
diff --git a/lib/sasl/doc/src/sasl_app.xml b/lib/sasl/doc/src/sasl_app.xml
index 8f92a22cf7..26b9bece2a 100644
--- a/lib/sasl/doc/src/sasl_app.xml
+++ b/lib/sasl/doc/src/sasl_app.xml
@@ -86,12 +86,6 @@
           <c>RELDIR</c> is used. By default, this is
           <c>$OTP_ROOT/releases</c>.</p>
       </item>
-      <tag><c><![CDATA[utc_log = true | false ]]></c></tag>
-      <item>
-        <p>If set to <c>true</c>, all dates in textual log outputs are
-          displayed in Universal Coordinated Time with the string
-          <c>UTC</c> appended.</p>
-      </item>
     </taglist>
   </section>
 
@@ -175,6 +169,12 @@
           <c>sasl_error_logger</c> to error reports or progress reports,
           or both. Default is <c>all</c>.</p>
       </item>
+      <tag><marker id="utc_log"/><c><![CDATA[utc_log = true | false ]]></c></tag>
+      <item>
+        <p>If set to <c>true</c>, all dates in textual log outputs are
+          displayed in Universal Coordinated Time with the string
+          <c>UTC</c> appended.</p>
+      </item>
     </taglist>
 
     <p>The error logger event handler <c>log_mf_h</c> can also still