question #1 Sahih al-Bukhari 5289, Book 68, Hadith 38 : What is the significance of the lunar calendar in Islamic practices and how does it affect the understanding of a month?

Allah’s Messenger (ﷺ) took an oath that he would abstain from his wives, and at that time his leg had been
sprained (dislocated). So he stayed in the Mashruba (an attic room) of his for 29 days. Then he came
down, and they (the people) said, “O Allah’s Messenger (ﷺ)! You took an oath to abstain from your wives for
one month.” He said, “The month is of twenty nine days.”