The Theory is that Batman (1989), Batman Returns, Batman Forever , Batman and Robin are set in a not too distant future (2022-2030) where the 2008 Wall Street finacial crash caused a Great Drepession that lasted 14 years and where the first Batman movie is first set is where the mafia has taken over the recently rebuilt Gotham and after 8 years Gotham becomes a Neo-Paradise. To Back-up my Theory there's a unused Batman (1989) poster that suggests that it was set in not too distant future and he used to be a vigilante before retiring.