Add more documentation for <Project>_SHOW_TEST_START_END_DATE_TIME

This is a super useful option when you want to know about timing of tests.

tribits/doc/build_ref/TribitsBuildReferenceBody.rst

@@ -1934,6 +1934,21 @@ did not get added, then this line will show why the test was not added
 ``CATEGORIES``, ``HOST``, ``XHOST``, ``HOSTTYPE``, or ``XHOSTTYPE``
 arguments).
 
+
+Enable advanced test start and end times and timing blocks
+----------------------------------------------------------
+
+For tests added using ``TRIBITS_ADD_ADVANCED_TEST()``, one can see start and
+end times for the tests and the timing for each ``TEST_<IDX>`` block in the
+detailed test output by configuring with::
+
+  -D<Project>_SHOW_TEST_START_END_DATE_TIME=ON
+
+The implementation of this feature currently uses ``EXECUTE_PROCESS(date)``
+and therefore will only work on many (but perhaps not all) Linux/Unix/Mac
+systems and not native Windows systems.
+
+
 .. _DART_TESTING_TIMEOUT:
 
 Setting test timeouts at configure time

tribits/doc/developers_guide/TribitsDevelopersGuide.rst

@@ -8499,15 +8499,16 @@ These options are described below.
 
   The cache variable ``${PROJECT_NAME}_SHOW_TEST_START_END_DATE_TIME``
   determines if the start and end date/time for each advanced test (i.e. added
-  with `TRIBITS_ADD_ADVANCED_TEST()`_) is printed or not with each test.  The
-  TriBITS default is ``OFF`` but a TriBITS project can change this default by
-  setting::
+  with `TRIBITS_ADD_ADVANCED_TEST()`_) is printed or not with each test.  If
+  set to ``TRUE`` this also causes in the timing for each ``TEST_<IDX>`` block
+  to be printed as well.  The TriBITS default is ``OFF`` but a TriBITS project
+  can change this default by setting::
 
     SET(${PROJECT_NAME}_SHOW_TEST_START_END_DATE_TIME_DEFAULT ON)
 
   The implementation of this feature currently uses ``EXECUTE_PROCESS(date)``
-  and therefore will only work on Linux/Unix/Mac systems and not Windows
-  systems.
+  and therefore will only work on many (but perhaps not all) Linux/Unix/Mac
+  systems and not Windows systems.
 
   NOTE: In a future version of CTest, this option may turn on start and end
   date/time for regular tests added with `TRIBITS_ADD_TEST()`_ (which uses a