- update description of isleap()

- add link to the datetime module

Doc/lib/libcalendar.tex

@@ -42,7 +42,8 @@ Returns the current setting for the weekday to start each week.
 \end{funcdesc}
 
 \begin{funcdesc}{isleap}{year}
-Returns \code{1} if \var{year} is a leap year, otherwise \code{0}.
+Returns \constant{True} if \var{year} is a leap year, otherwise
+\constant{False}.
 \end{funcdesc}
 
 \begin{funcdesc}{leapdays}{y1, y2}
@@ -108,5 +109,8 @@ an epoch of 1970, and the POSIX encoding.  In fact,
 
 
 \begin{seealso}
+  \seemodule{datetime}{Object-oriented interface to dates and times
+                       with similar functionality to the
+                       \refmodule{time} module.}
   \seemodule{time}{Low-level time related functions.}
 \end{seealso}