The problem is the Google JSON output of the Google Calendar API . FullCalendar converts feeds such as
http://www.google.com/calendar/feeds/usa__en%40holiday.calendar.google.com/public/basic
in
http://www.google.com/calendar/feeds/usa__en%40holiday.calendar.google.com/public/full?alt=json-in-script&callback=?
in gcal.js on line 49
url: sourceOptions.url.replace(/\/basic$/, '/full') + '?alt=json-in-script&callback=?',
There seems to be no indication that the specifications have changed. So I guess there is a problem on Google.
EDIT
More here
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