Set the custom initial date on FullCalendar based on a field in the current node
So this and two additional Content Node Fields edit worked for me. Starting around line 629 in includes/views/fullcalendar.fullcalendar.inc, I changed to the following. Don't forget to add two additional fields to your Content Type with machine names field_default_calendar_year and field_default_calendar_month.

Update on project's issues list: Patch Submitted, Requested Review

See Patch code: http://drupal.org/files/fullcalendar-7.x-2.x-custom_init_date_1.patch