The Calendar Man, last seen in these pages back in 1979, returns for a three-part story, which begins in Batman 384 (June 1985), by Moench, Hoberg and Nebres.
This is one of the tales to cameo the Monitor and Lyla, preceding the events of Crisis on Infinite Earths, following their appearance in World’s Finest Comics. The Monitor provides the Calendar Man with the contract to kill Robin, originated by hoods who want to hurt Batman, and get him off their backs.
The story really builds up the character, and makes the Calendar Man a far more serious villain than he had ever been hon to be previously.
In fact, he comes off far better than Batman, who is busy mooning over Catwoman and Nocturna, while bemoaning the end of his relationship with Vicki Vale, while Alfred tries to push him into a romance with his daughter, Julia.
Calendar Man decides to kill Robin on the first day of Spring, but to spend the intervening days committing other robberies, themed to the various holidays between then and the beginning of the year. This gives him plenty of opportunity to show off a variety of costumes and themed weapons. That must be why he does it. Certainly he just make things harder on himself by giving the heroes so many opportunities to catch him.
The story continues in the next issue of Detective.