v1.1.5 and calendar hack...HELP!

I have returned to v1.1.5 for several reasons, and after installing the calendar hack (fresh install, v1.03) and re-checking it, I see nothing wrong but still I get the following error when I try to call up calendar.php in my browser:

Parse error: parse error, expecting `'['' or `PHP_CLASS_OPERATOR' or `'}'' in
/home/httpd/html/newboard/calendar.php on line 129

This is the block of code from calendar.php containing the line in question:

line 128 --- $prevmonth = $month-1;
line 129 --- $prevmonth = "${month.$prevmonth.name} $year";
line 130 --- $monthtext = "${month.$month.name} $year";
line 131 --- $nextmonth = $month+1;
line 132 --- $nextmonth = "${month.$nextmonth.name} $year";

Can anyone tell me what's wrong? I know v2.0.0 has the calendar built-in, but (pardon me for saying so) I don't like v2.0.0, and will not be using it.

I know next to nothing about php coding, so any help would be very much appreciated.

Upgrade to 1.1.6 so we can support you.

But you are a little late really as the author has chosen not to support that hack anymore meaning no one will help.

ok, thanks John....I'll look into going to v1.1.6
...although, the lazy bugger in me has to confess that redoing all the hacks and customization is a dreaded thought. But, If I gotta then I gotta.