Use _datetime docstring if _datetime is available.
diff --git a/Lib/datetime.py b/Lib/datetime.py
index 7b7b8aa..19f20e7 100644
--- a/Lib/datetime.py
+++ b/Lib/datetime.py
@@ -2085,3 +2085,8 @@
_days_before_year, _days_in_month, _format_time, _is_leap,
_isoweek1monday, _math, _ord2ymd, _time, _time_class, _tzinfo_class,
_wrap_strftime, _ymd2ord)
+ # XXX Since import * above excludes names that start with _,
+ # docstring does not get overwritten. In the future, it may be
+ # appropriate to maintain a single module level docstring and
+ # remove the following line.
+ from _datetime import __doc__