diff --git a/src/corelib/configure.cmake b/src/corelib/configure.cmake
index 71812527917..e588b2b8cdd 100644
--- a/src/corelib/configure.cmake
+++ b/src/corelib/configure.cmake
@@ -1017,6 +1017,8 @@ qt_feature("timezone_tzdb" PUBLIC
     LABEL "std::chrono::tzdb QTZ backend"
     PURPOSE "Provides support for a timezone backend using std::chrono."
     CONDITION TEST_chrono_tzdb
+    # See QTBUG-127598 for gcc's libstdc++'s deficiencies.
+    # Update src/corelib/doc/src/cpp20-overview.qdoc before enabling this:
     AUTODETECT OFF
 )
 qt_feature("datetimeparser" PRIVATE
diff --git a/src/corelib/doc/src/cpp20-overview.qdoc b/src/corelib/doc/src/cpp20-overview.qdoc
index e24b72d74ad..55beaf366c9 100644
--- a/src/corelib/doc/src/cpp20-overview.qdoc
+++ b/src/corelib/doc/src/cpp20-overview.qdoc
@@ -24,11 +24,20 @@
     representations}, such as the \l
     {https://en.cppreference.com/w/cpp/chrono/system_clock} {system_clock} and
     its \l {https://en.cppreference.com/w/cpp/chrono/time_point} {time_point}
-    types. When Qt is built with C++20, it can now make use of these additions.
+    types. It also now provides access to the IANA database of \l
+    {https://en.cppreference.com/w/cpp/chrono#Time_zone} {timezone-related
+    information}. When Qt is built with C++20, it can now make use of these
+    additions.
 
     QDate and QDateTime now support conversion to and from the various calendar,
     date and date-time types, along with addition of \l
     {https://en.cppreference.com/w/cpp/chrono/duration} {duration
     types}. QTimeZone now supports construction from a \l
     {https://en.cppreference.com/w/cpp/chrono/time_zone} {time_zone}.
+
+    QTimeZone can also, when built with feature \c timezone_tzdb enabled, use
+    the C++20 \l {https://en.cppreference.com/w/cpp/chrono/tzdb} {tzdb}
+    facilities in place of platform-specific backends to access timezone
+    information. This remains experimental in Qt 6.9 as some standard library
+    implementations do not faithfully represent the IANA data for timezones.
 */