title: group by a date range in google spreadsheet
body: <p>I'm making a sheet in google Spreadsheet and I'd like some help with you. I want to group some values based on a date range (from 25/12/2015 to 25/01/2015, for example). The interval will be always from 25 of one month to 25 of the another. Is there anyway I could do this automatically? I already did it grouping by month, but could't in a date range.
  This is an example sheet I'm working:
  <a href="https://docs.google.com/spreadsheets/d/1jFEAalIo378Q3DVZ4aJKGCADy3dzjs8nJr5fm55eNvg/pubhtml" rel="nofollow">https://docs.google.com/spreadsheets/d/1jFEAalIo378Q3DVZ4aJKGCADy3dzjs8nJr5fm55eNvg/pubhtml</a></p>
  
  <p>Tks!</p>
  
  <p>Rafael.</p>