The Storyteller trophy/achievement is where you, Batman, have to go into the bottom floor of the courthouse and speak with Calendar Man on specific holidays, resulting in him describing a crime he committed on that holiday in the past. The game uses the internal clock of whatever system you're playing on, so if you play the game on Christmas (or tell your system that it's Christmas by setting the clock manually instead of through the internet), Calendar Man will tell you a story about a crime he committed on Christmas. It's a cool Easter egg that gets you some good, violent stories and a trophy/achievement.

Arkham City isn't the first game to use a console's clock to trigger special events like this, but it's one of the best uses I've seen. I know that Animal Crossing does this to a much larger extent, too.

Did anyone else bother getting this achievement? Did you do it in real-time or did you change the clock? What other cool uses of this mechanic have you seen?

The Storyteller trophy/achievement is where you, Batman, have to go into the bottom floor of the courthouse and speak with Calendar Man on specific holidays, resulting in him describing a crime he committed on that holiday in the past. The game uses the internal clock of whatever system you're playing on, so if you play the game on Christmas (or tell your system that it's Christmas by setting the clock manually instead of through the internet), Calendar Man will tell you a story about a crime he committed on Christmas. It's a cool Easter egg that gets you some good, violent stories and a trophy/achievement.

Arkham City isn't the first game to use a console's clock to trigger special events like this, but it's one of the best uses I've seen. I know that Animal Crossing does this to a much larger extent, too.

Did anyone else bother getting this achievement? Did you do it in real-time or did you change the clock? What other cool uses of this mechanic have you seen?

Halo 4 has an achievement where you have to jump a Warthog at midnight.

Halo 4 has an achievement where you have to jump a Warthog at midnight.

Cool, I guess I'll keep that in mind when I get around to Arkham City. This reminds me of playing Costume Quest on Christmas to get an achievement.

I really dislike the look they gave Calendar Man in the game. Best look he had was in The Long Halloween. Anyways, Best use of Clock Mechanic has got to go to MGS 3. I won't spoil it but those who played the game know what I am talking about. Another cool use of actual time frame was in Demon's Souls and how Atlus used to turn the whole world's tendency Pure Black for Halloween and Pure White for Christmas.

I remember in Simpsons Road Rage that certain cars would unlock on certain days, so like Apu would have an Christmas Sports Car on 25/12. Can't remember if they were reskins or brand new cars.  
Also, I started to cheat on that achievement but then I couldn't be bothered to finish it. I'll be the first guy in line talking about how Batman Arkham City is one of the best games ever, but urgh. Anyway, congratz on getting the achievement.  
Does GiantBomb have a concept page for this feature in video games? Time sensitive content I guess it would be called.

In order to access the Insomniac Museum in one of the old Ratchet games, you had to be in a specific place at a specific time.

@CharlesAlanRatliff: Have you read Batman: Dark Victory?

I didn't even know that achievement existed!

Brothers in Arms: Hell's Highway has an achievement for playing the game on the anniversary of Operation Market Garden.