Today marks the American federal holiday of Labor Day and another opportunity to visit Calendar Man in https://www.trueachievements.com/Batman-Arkham-City-xbo....htm
on the road to the legitimately earning the following achievement:
Labor Day celebrates the economic and social contributions of workers in the United States and is a public holiday there, so for all you holidaying Americans today, happy Labor Day
! For everyone else, happy...Monday
The next Calendar Man date is October 31st (Halloween).