Have 12 murderous dates with Calendar Man

Achievement Value: 10

In the Soloman Wayne Courthouse (the courthouse in the beginning of the game when you rescue Catwoman, who is hanging over a pit of acid, from TwoFace), you can talk to the Calendar Man, who is locked up in the basement. You will notice a calendar on the wall next to his cell with 12 days circled. January 1st (New Years Day) February 14th (Valentines Day) March 17th (St. Patrick's Day) April 1st (April Fools Day) May 13th 2012 (or May 8th 2011) (Mothers Day) (Be sure to adjust the year) June 19th 2011 (Father's Day) (Be sure to adjust the year) July 4th (Independence Day) August 16th (Feast Day of Saint Roch) September 5th (Labor Day) October 31st (Halloween) November 24th 2011 (Thanksgiving) (Be sure to adjust the year) December 25th (Christmas)

If you talk to Calendar Man on each of these days, he will tell you a story about someone he murdered on that day. The corresponding month will also be crossed off the calendar.

To get this achievement quickly, disconnect your console from the internet, and change the consoles system date. Then speak to Calender Man, and then walk out the back door to get the game to save.