You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Pope_John_XXIII

Context:
On 25 May 1963, the pope suffered another haemorrhage and required several blood transfusions, but the cancer had perforated the stomach wall and peritonitis soon set in. The doctors conferred in a decision regarding this matter and John XXIII's aide Loris F. Capovilla broke the news to him saying that the cancer had done its work and nothing could be done for him. Around this time, his remaining siblings arrived to be with him. By 31 May, it had become clear that the cancer had overcome the resistance of John XXIII – it had left him confined to his bed.

Question:
When was it clear that the cancer had overcome the resistance of John XXIII?

31 May