In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
Q: What is the one event that is conditional for the deacons in the event described?, Context: When not celebrating Mass but still serving a liturgical function, such as the semiannual Urbi et Orbi papal blessing, some Papal Masses and some events at Ecumenical Councils, cardinal deacons can be recognized by the dalmatics they would don with the simple white mitre (so called mitra simplex).
A:
When not celebrating Mass