They switch somewhere between 1860 and 1936
(Ignore all these, ) There no exact dates of when the events in history happen but only the year it happened. Eventhough there's an exact date, no ones know if it true because we are in the 2000 and history in books always start at 1700, none of us ever seen it happened LIVE cuz we r not even born, can't confirm if the date is accurate.
