Google::Graph first bar (es. month) does not respect the start of the chosen date

[eniocarboni]

Suppose we use The Google::Graph plugin (date_resolution="month") and my first query is

# now use range date:
<MY_EPRINTS_BASE_URL>/cgi/stats/report/?range=6m&view_range=View
# render date: Set 7, 2015 - Mar 7, 2016

the render graph on September is from 07 Set to 30 Set, as i expected and this is good,

then the second query is

# now use "from date" and "to date"
<MY_EPRINTS_BASE_URL>/cgi/stats/report/?from=2015-09-07&to=2016-03-07
# render date as before: Set 7, 2015 - Mar 7, 2016

but the render graph on September is from 01 Set to 30 Set, all month

This behavior, unwanted, is given by the "sub Google::Graph.pm::get_data" from line 50 to 65
I think that these lines could be eliminated.