It depends on how you do it. The most surgical way to remove history visits is to open the Library window using "Show All History" or Ctrl+Shift+H and then get a list of what you want to clear. For example, you usually will find time bands in the left column so you can view history from more than a few months ago. Now... it is a little confusing because the Last Visit date will show the most recent date you visited the site rather than the date you visited the site in that period. You might want to scroll down and begin your selection with a site you haven't visited since back in the day. Then you can press Shift+End to select from that point all the way down to the end of the list and tap the Delete key. Bye bye history. Did I mention there's no Undo for that? As far as I know, there's no Undo for that. Also, this may take a long time if you are deleting thousands of entries. If you want something that's potentially more accurate, you could look at the many add-ons for managing or pruning history.