Today the Holy Father at his general audience spoke about the week of prayer for Christian unity, see here, in the text that was published the past tense was used, those who heard it, including the venerable Fr Z say he used the present tense, thus:
In the liturgy of the ancient Church, after the sermon the main celebrant -- the bishop or the president of the celebration -- used to say: "Conversi ad Dominum" (turn to the Lord). Then he and everybody else stand up and turn themselves toward the East. All want to look toward Christ. Only if converted, only through this conversion to Christ, in this common look at Christ, can we find the gift of unity.
This little passage is very significant in the light of the ad orientem celebration in the Sistine chapel
read the whole text here