iCal feeds from the Calendar page will include the past 2 months and the next 12 months. These are "rolling" feeds so they will update to include new events. 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 can take up to 24 hours for the feed to sync with the new events.
Other calendar feeds, such as those under My Day: Schedule & Performance, include the next 60 days instead of 12 months.