displaying months from cells as their text (not numerical)

G'Day,

Please refer to the attached screenshot of my working spreadsheet for help.

Please avert your attention to line 86 (month2). The formula contained within these cells equals =MONTH(C84) [the date 2 cells above it]... to which I've formatted the cell to "mmmm" and it displays "January" across the board. Can anyone explain why this is occuring and how I can fix it please? I'm aiming to graph this information and can't accurately do it using the moving monthly system i've put in place if I can't change the months dynamically like this.

Secondly, and on a side note. Line 84 currently takes todays date (not currently todays date in the example screenshot) (=TODAY()), and to get to the previous 13 months I deduct 31 days. I can foresee this as being a problem further down the track especially when leap years come into play. Is there a function in Excel where I can simply deduct 1 month from another? =MONTH(C84)-1 ?