Clarify note about using %U and %W with strptime().
diff --git a/Doc/lib/libtime.tex b/Doc/lib/libtime.tex
index 3b4ec7e..7a13879 100644
--- a/Doc/lib/libtime.tex
+++ b/Doc/lib/libtime.tex
@@ -272,8 +272,9 @@
The range really is \code{0} to \code{61}; this accounts for leap
seconds and the (very rare) double leap seconds.
\item[(3)]
- \code{\%U} and \code{\%W} are only used in calculations when the day of the
- week and the year are specified.
+ When used with the \function{strptime()} function, \code{\%U} and \code{\%W}
+ are only used in calculations when the day of the week and the year are
+ specified.
\end{description}
Here is an example, a format for dates compatible with that specified