Even the month here is approximate. But we know that the event took
place "some months" before the raid on Maracaybo in August
(Chapter XVI). And it can be no earlier than May, when Blood
returned to Tortuga from his first voyage. Furthermore, after that
return, Blood met Levasseur, agreed to his proposal (articles were drawn
up "within a week"), set sail, and the rescue was the following
day. We also know that Blood was in San Juan by June 3.
We could fix the date exactly if we had weather records from the
Caribbean in 1687, wherein to look up the date of the hurricane. I
have googled and googled for such records without success. Alas.