Note: Perform this while offline (not logged into Xbox Live or PlayStation Network as your system date is automatically set via the internet). Set the date of your console to a holiday date (for example, January 1, February 14, etc.) and load a saved game file where the story progress is past rescuing Catwoman. Enter the courthouse and speak to Calendar Man in the basement. He will tell you a story about the current month's holiday and tell you to return for the next month. Save the game by leaving the building. Exit to the system settings, then manually change the date to the following holiday. Repeat the process until you have cycled through the entire calendar year. The calendar on the wall next to his cell will highlight the holiday dates for the current year and scribble out which months you have already spoken to Calendar Man about.