Documentation is your friend ;)
>>> date = QtCore.QDate.fromString('20130916', 'yyyyMd')
# PySide
>>> date.toString('MMMM d, yyyy')
u'September 16, 2013'
# PyQt4
>>> date.toString('MMMM d, yyyy')
PyQt4.QtCore.QString(u'September 16, 2013')
>>> unicode(date.toString('MMMM d, yyyy'))
u'September 16, 2013'