Date matching range over end of month

I have a file that arrives every Wednesday. I can successfully match the date to rename the file every week unless the date range spans the end of the month. For example, most dates in the file content are in the format July 2-8, 2014. But, at the end of the month the date range is July 30 - August 5, 2014.
My matching rule is Contents contain match xdaterange where xdaterange is defined as [December] [...] [31], [1999]. So, it renames the first file to 2014-07-08. The second one renames to 2014-07-05 with the incorrect month. Because the content line changes by adding the second month name only when spanning end of month, I do not have a solution to parse the date. Any ideas?
My matching rule is Contents contain match xdaterange where xdaterange is defined as [December] [...] [31], [1999]. So, it renames the first file to 2014-07-08. The second one renames to 2014-07-05 with the incorrect month. Because the content line changes by adding the second month name only when spanning end of month, I do not have a solution to parse the date. Any ideas?