Given the question: Question: "What is the time constraint that a pope can reveal the identity of an in pectore cardinal?"  Context: "If conditions change, so that the pope judges it safe to make the appointment public, he may do so at any time. The cardinal in question then ranks in precedence with those raised to the cardinalate at the time of his in pectore appointment. If a pope dies before revealing the identity of an in pectore cardinal, the cardinalate expires."  Answer:
The answer is:
at any time