iCalendar API in Java

http://sourceforge.net/projects/biweekly/
http://sourceforge.net/p/biweekly/wiki/Home/

http://wiki.modularity.net.au/ical4j/index.php?title=Main_Page
https://code.google.com/p/ical4j/

http://valermicle.blogspot.sg/2009/02/i-was-searching-for-documentations-on.html

https://developers.google.com/api-client-library/java/apis/calendar/v3

https://code.google.com/p/caldav4j/