Document and test the UTC time feature

README.md

@@ -237,6 +237,16 @@ Examples:
 [{server,{pid, ["(", pid, ")"], ["(Unknown Server)"]}}] -> user provided server metadata, otherwise "(<?.?.?>)", otherwise "(Unknown Server)"
 ```
 
+Universal time
+-----------------
+Lager reads the `sasl` application's configuration, if `utc_log` is set to `true`, the times will be displayed in UTC format.
+
+Example:
+
+```
+application:set_env(sasl, utc_log, true).
+```
+
 Error logger integration
 ------------------------
 Lager is also supplied with a `error_logger` handler module that translates

test/lager_test_backend.erl

@@ -696,6 +696,25 @@ lager_test_() ->
                         ?assertError(badarg, lager:md("zookeeper zephyr")),
                         ok
                 end
+            },
+            {"dates should be local by default",
+                fun() ->
+                        lager:warning("so long, and thanks for all the fish"),
+                        ?assertEqual(1, count()),
+                        {_Level, {_Date, Time}, _Message, _Metadata}  = pop(),
+                        ?assertEqual(nomatch, binary:match(iolist_to_binary(Time), <<"UTC">>)),
+                        ok
+                end
+            },
+            {"dates should be UTC if SASL is configured as UTC",
+                fun() ->
+                        application:set_env(sasl, utc_log, true),
+                        lager:warning("so long, and thanks for all the fish"),
+                        ?assertEqual(1, count()),
+                        {_Level, {_Date, Time}, _Message, _Metadata}  = pop(),
+                        ?assertNotEqual(nomatch, binary:match(iolist_to_binary(Time), <<"UTC">>)),
+                        ok
+                end
             }
         ]
     }.