question #3 Sahih Muslim 1084a, Book 13, Hadith 27 : How does this narration illustrate the flexibility in the length of a lunar month?

) He came to us on the twenty-ninth day, whereupon we said: It is the twenty-ninth (day) today. Thereupon he said: So far as the month is concerned, (and he, with a view to explaining it) flapped his hands thrice, but held back one finger at the last turn.