When using the iCal feed, it will only show 2 months back and 12 months forward for a total of 14 months, but it is a rolling feed so it will update to include new events.
The new Calendar (released July 1st 2015) will allow past events to display from the iCal feed.
It can take up to one (1) hour for the new events to sync into the calendar feed for the User on their Calendar. This can also be impacted by the Calendar Client as well. For example Google Cal states it can take up to 24 hours for the feed to sync with the new events.