Calendar date from formula

Hi all,

I'm not really sure how to explain this, but what I am trying to achieve is to get a calendar layout using an array formula. The formula I'm using is from a workbook that I had found on the web and it works perfectly. It was in a general calendar layout when I downloaded it and I have adapted it to run from day 1 - the last day in a month from left to right.

My starting day for each week is Monday (the original workbook used Sunday). The problem though is, when I get to a month that starts on a Sunday, it starts populating from the first Monday, and thus losing the 1st day of that month. I have attached an example.

Thanks.