Download History Cleaner (Eraser) — Andy Portmen

"Download History Cleaner" is the easiest way to clear your browser download history for a specified period. You can define the custom period on the options page. Also, you can define the area (zone) in which you want the data to be cleared.

For a more comprehensive cleaner try my eCleaner
https://addons.mozilla.org/firefox/addon/ecleaner-forget-button/

Using this extension it is possible to delete the download history of three different zones:
1. Normal websites,
2. Protected websites (not supported in Firefox yet),
3. Extension zone (not supported in Firefox yet)

Definitions:
-> Extensions zone: Extensions and packaged applications a user has installed (not yet supported in Firefox)
-> Protected websites zone: Websites that have been installed as hosted applications (not yet supported in Firefox)

For bug reports please visit:
https://github.com/andy-portmen/ecleaner

For FAQs please visit:
https://add0n.com/ecleaner.html?from=downloads-cleaner