Hello,

I'm afraid that clearing old history but keeping recent history is impossible. You can only do the opposite: clearing recent history, but keeping old history. This can be done through the 'Forget' button.

maybe Mozilla geniuses can fix this issue.

You can clear older history in the History Manager. Type a common character like a colon (:) in the search bar and start selecting links from the bottom up and press the Delete key to remove the selected links.

You can use Shift + Page Up to select more items at the time.

Expire history by days {web link} Allows to expire history older than a fixed amount of days.