Archer is the opposite of science fiction.
It seems like modern day, but also they keep using tech that is systemic to the 1970s and 1980s. Well not the real seventies and eighties... If old Bond films were real.
And yet then they also sometimes use technology that seems futuristic even for us. There's been a running cyborg subplot for 2-3 seasons now. It's kind of a running joke on the show that there's no real way to know when it actually takes place.