3. One day, three young men met at the library, and one of them said: "Starting today, I will come to the library once a day." The second person said: "I will come to the library once every two days." The third person stated that the library is closed on Sundays and does not open. One of the young men suggested that if any of them were to come to the library on a day it is closed, they would be allowed to skip that day and come the next day, and their schedule for visiting the library would start from that day onward. The young men agreed to this.

They met again at the library on a Monday. Try to determine on which day the conversation recorded above took place.
（Hint: Use a "logic table" to solve this problem, and note that the conversation recorded above took place on a Saturday, 9 days before their second meeting,）