You can remove the months in the History Manager (Library)

• (Firefox) > History > Show All History

• http://kb.mozillazine.org/Viewing_the_browsing_history_-_Firefox

First of all I would like to say thanks for responding to my question so quickly,I appreciate it.I guess my question wasn't clear enough.In older versions of FF,you go into about:config and change the number of days total that history would be kept.For example Today and Yesterday,or just Today,but not for months at a time like it is now, and not be configurable.Again thanks for your help,and hopefully you or someone else will be able to answer my question.Thank you.

The prefs browser.history_expire_days and browser.history_expire_days_min are removed in Firefox 4+ versions and replaced with a single places.history.enabled pref to remember history or disable the history.

There is no time limit in Firefox 4+ versions for the history.
Firefox determines automatically how many pages can be kept without affecting the performance. You can see the current value via the pref places.history.expiration.transient_max_pages on the about:config page.
You now need to remove older history manually as you can no longer set a limit.
That is why I posted above that you can remove history in the Library.

See:

• http://blog.bonardo.net/2010/01/20/places-got-async-expiration

Again I want to thank you for your rapid response.That was not the answer I wanted to hear,but I do appreciate your help.You would think that FF would leave well enough alone with something that worked very well for many years.They should be giving us more choices not less. Once again thank you very much for your quick response.

I guess you will be able to expire history older than nnn days in Firefox 7, see last link in the link cor-el posted pointing to and a comment there say FF7.

• http://blog.bonardo.net/2011/08/05/a-couple-add-ons-for-places-maintenance

To expand on manually do your search and sort by date then make your selections by click, Ctrl+click, or Shift+click to the left of the favicon in history sidebar, or history library list, and if everything in search is to be deleted you can use Ctrl+A to select all.

• Selecting history items in Viewing the browsing history - Firefox (MozillaZine KB)
• Library Viewing the browsing history in Viewing the browsing history - Firefox (MozillaZine KB)

You may be looking at combined entries (months, older than six months) though so don't really know how that will work out for you, but older items count less anyway in frecency rating used for the AwesomeBar feature.