Use \ldots, not \dots. The info process doesn't know about \dots.

Doc/lib/libcalendar.tex

@@ -19,7 +19,7 @@ Return the number of leap years in the range
 
 \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}