Legacy Cumulus 1 release 1.9.4 (build 1099) - 28 November 2014
(a patch is available for 1.9.4 build 1099 that extends the date range of drop-down menus to 2030)
Download the Software (Cumulus MX / Cumulus 1 and other related items) from the Wiki
Not sure what script you are using, but you can have your script change the ranges of both daily and monthly values to adjust to what is actually available.
Since you are using a script to build the array used by the graphs, you can easily tell what the min and max values are and then adjust the min/max values for each section of your chart to match.