EDIT: (for Firefox) If you can't remember the date and want to know, you can get it by opening your firefoxes profile directory -> find places.sqlite -> open it with sqlite3 command line or with some gui software and execute this:
SELECT datetime(visit_date/1000000,'unixepoch') AS visit_date, url, title
FROM moz_places, moz_historyvisits
WHERE moz_places.id = moz_historyvisits.place_id AND url LIKE '%https://www.reddit.com/settings/data-request%';