I've always found that Total Commander is the best solution to multiple name changes. It allows you to put prefixes, suffixes or just rename the files completely, as well as through using naming rules and even regular expressions to find certain parts of the name.
If everything were just the last 4 characters of the filename with a prefix, that would be easily done. If you wanted it to logically analyse what the date was in the middle, I don't think there's any program that could natively do that, but you could make a custom script to do that for you. (or just manually choose all the files from August and do them in one batch, with other months in their own batches)
It's shareware, but completely free and with no caps or limitations if you don't pay. You can download it here: http://www.ghisler.com/