Julian Day, better known as the Calendar Man, is a character that is referenced in Batman: Arkham Asylum, physically appears in Batman: Arkham City, and makes cameo appearances in Batman: Arkham Origins and Batman: Arkham Knight. A brutal and psychotic, but highly intelligent serial killer who plots his murders around holidays, with the grisly nature of his victims' deaths often serving as irony towards the nature of the respective holiday, Day does not discriminate against any potential victim on any holiday.