SF 639138, Ref. calendar module in time docs by John J Lee
Will backport.
diff --git a/Doc/lib/libtime.tex b/Doc/lib/libtime.tex
index 598278a..308152d 100644
--- a/Doc/lib/libtime.tex
+++ b/Doc/lib/libtime.tex
@@ -322,4 +322,7 @@
\seemodule{locale}{Internationalization services. The locale
settings can affect the return values for some of
the functions in the \module{time} module.}
+ \seemodule{calendar}{General calendar-related functions.
+ \function{timegm()} is the inverse of
+ \function{gmtime()} from this module.}
\end{seealso}