Altering format.date in bst to place parentheses around year

I would like to add parentheses to the year in the bibliography of a paper (i.e., Kyle, A. S. (1985). etc.). Unfortunately, the journal .bst file is not quite correct on this point. The link to the .bst file is at: http://ift.tt/1tC2vVm

I have been unsuccessful altering the format.date function to accomplish this based on related questions. Below is a MWE:

\documentclass[11pt, letterpaper,doublespacing]{article} 
\usepackage{setspace} 
\makeatother 
\usepackage{ntheorem} 
    \RequirePackage{amsmath,amsfonts,amssymb,xcolor,graphicx,natbib,booktabs,geometry,chngcntr,comment,array,dcolumn,subfig, lscape, longtable}
\usepackage[title]{appendix}
\usepackage[labelfont=bf,labelsep=newline]{caption}  %Make Table and Figure bold
\theoremstyle{plain}  %COMMENTED 10/6/14

\begin{document}
\cite{Kyle_Econ_1985} is a seminal paper.

\bibliographystyle{rfs}
\bibliography{mwe_bib}

\end{document}

Here is the .bib entry:

@ARTICLE{Kyle_Econ_1985,
  author = {Kyle, Albert S.},
  title = {Continuous Auctions and Insider Trading},
  journal = {Econometrica},
  year = {1985}, 
  volume = {53},
  pages = {1315--1336},
}