Use \ldots, not \dots. The info process doesn't know about \dots.
diff --git a/Doc/lib/libcalendar.tex b/Doc/lib/libcalendar.tex
index 1f3931e..79515b1 100644
--- a/Doc/lib/libcalendar.tex
+++ b/Doc/lib/libcalendar.tex
@@ -19,7 +19,7 @@
\begin{funcdesc}{weekday}{year, month, day}
Returns the day of the week (\code{0} is Monday) for \var{year}
-(\code{1970}--\dots), \var{month} (\code{1}--\code{12}), \var{day}
+(\code{1970}--\ldots), \var{month} (\code{1}--\code{12}), \var{day}
(\code{1}--\code{31}).
\end{funcdesc}