How to change margins when using termcal

I'm using term cal on a syllabus. I want to type a lot of text within the columns of my syllabus calendar, so I want to use as much of the width of the page as possible for those columns (on an 8.5 inch page, I'd like to use at least 7.5 of those inches).

The default margins are wider than that (which is fine for the rest of the syllabus, but not for the calendar part).

So far, I've figured out (I think) how to change the width of the calendar with

\calwidth7.5in

But then it prints with the normal left margin and the calendar columns running to the very edge of the right side of the page. I want the calendar centered, but as wide as possible.

I tried to change the margins for just this part of the page with the changepage package. So now I call that in the beginning of the document

\documentclass[12pt]{article}
\usepackage{termcal}
\usepackage{changepage}
\usepackage[colorlinks=true,pagebackref,linkcolor=blue]{hyperref}
\textwidth=7in
\textheight=9.5in
\topmargin=-1in
\headheight=0in
\headsep=.5in
\hoffset  -.85in

Then just before the calendar, I try to increase the margins:

\paragraph*{Course Calendar:}
\hoffset  0in

\begin{adjustwidth}{-1in}{-1in}

\begin{calendar}{01/12/2015}{17} 
\centering
\setlength{\calboxdepth}{2.3in}
% my failed attempt at changing width  
\calwidth7in

Then, after the end of the calendar, I end the new margins:

\end{calendar}

\end{adjustwidth}

\end{center}
\end{document}

But this doesn't seem to do anything. And Kile (which I'm using to edit and produce the pdf) complains that

/begin{document} ended by \end{center}. \end{center}

The calendar environment requires at least one \calday command for typesetting, otherwise it complains.

Amongst other issues:

• Either \begingroup \centering .... \endgroup
• \begin{center}...\end{center} for the 'same' effect, however with additional spacing above and below.
• Use \usepackage{geometry} package (not done in my solution) to change the page geometry rather than hacking the lengths directly

\documentclass[12pt]{article}
\usepackage{termcal}
\usepackage{changepage}
\usepackage[colorlinks=true,pagebackref,linkcolor=blue]{hyperref}
\textwidth=7in
\textheight=9.5in
\topmargin=-1in
\headheight=0in
\headsep=.5in
\hoffset=-.85in

\begin{document}

\paragraph*{Course Calendar:}
%\hoffset  0in

\begin{adjustwidth}{-1in}{-1in}

\begingroup
\centering
\begin{calendar}{01/12/2015}{17} 
\calday[Monday]{\classday}
\setlength{\calboxdepth}{2.3in}
% my failed attempt at changing width  
\calwidth7in

\end{calendar}
\endgroup
\end{adjustwidth}

\begin{center}
\begin{adjustwidth}{-1in}{-1in}
\begin{calendar}{01/12/2015}{17} 
\calday[Monday]{\classday}
\setlength{\calboxdepth}{2.3in}
\calwidth7in
\end{calendar}
\end{adjustwidth}
\end{center}
\end{document}