Let us focus on the auxiliary have. Would it make antecedent time extents altogether? Antecedent time extents always would be relative to the head time. To shape up a good idea for head verbs and time, we can venture common sense, as also in literature. The common sense truth here is that it can take real time to make hypotheses, but hypothetical time could never be the same as real time.
. . . Let us think about Madame Règle. She has the potential to have lunch at Latimer Sauf’s restaurant every day. He always has a table for his friends and she has enough money. However, her work with Paris haute couture designers often keeps her over the lunchtime. Her coming to lunch is probable, but not certain. CERTAINTY requires both potentiality and probability. Let us think about Monsieur Sauf’s birthday. Madame Règle will come to meet him. It is certain.