Love it, works really well, thank you. My only suggestions for improvement might be;

The Days and Times seem to run/ascend from left to right rather than right to left. For a native English speaker this is a little disconcerting. If I could propose it would feel a lot more intuitive if the Dates and Times ran from Left to Right as is expected.

The history box feels a little cramped too on Firefox- I really like the Chrome version of this extension that opens in a new tab. For me it feels a lot more comfortable seeing all that history in a larger space