The Pope, who himself participated in Vatican Council II as an expert, noted that "many memories come to mind, memories inscribed in each of our hearts, of the period of the Council which was so lively, so rich and so fruitful. However I do not wish to dwell upon this for too long, ... I would merely like to recall how a word launched by Blessed John XXIII, almost as if to establish a programme, resurfaced continually during the course of the conciliar sessions: the word 'aggiornamento'.
"Fifty years on from the opening of that solemn gathering of the Church", Benedict XVI added, "some people may ask themselves whether that term was perhaps, from the very beginning, not entirely appropriate. Choice of words is something that can be discussed for hours without reconciling contrasting opinions, for my part I am convinced that the intuition which Blessed John XXIII summarised in that word was and remains correct. Christianity must not be considered as 'something that has passed', nor must we live with our gaze always turned back, because Jesus Christ is yesterday today and forever. Christianity is marked by the presence of the eternal God, Who entered into time and is present in all times, because all times are brought forth of His creative power, of His eternal 'today'.
The full address may be read here.
An excellent interview with Cardinal Wuerl on the Council, aggiornamento, re-evangelization, secularization etc. can be heard here.