These docs are for an old release. Info on upgrading to version 2/3
edit doc

parseDate

Parses a string into a Date object.

$.fullCalendar.parseDate( string ) -> Date

The string may be in ISO8601 format, IETF format, or a UNIX timestamp (in either integer or string form).

IETF format only correctly started working in version 1.3.2.