First place the files in any directory (for one section of code you may need to edit if you do not put it in: "%YaBB installation%/calendar/" directory)
Then edit the as follows:

You MUST add this to the Default.html page (if you have another name for the main template page edit it):

You MUST add this to the pages .CSS file(s) (you may edit as pleased):

You MUST edit the Subs.pl file as follows:
Find this line: "for(my $i = 0; $i <= $#yytemplate; $i++) {"
Above that line add this:

You MUST edit the Paths.pl file and add this line (preferably at the bottom, but not past the "1;"):

LAST but not least; Edit your Default.html page (if you have another name for the main template page edit it) and add this where ever you want the calendar to on the page:

 

If you have problems installing or if I missed something, please email me at: thegreatall@gmail.com (please note: this is mod for YaBB2 is not finished)