WHIT STILLMAN begins his ''Metropolitan'' with the advisory that the film takes place ''not so long ago,'' and it is good he does. If he didn't, you'd wonder where these people live, on which planet, in whose time?
''Metropolitan'' is Stillman's first feature film. It was shown as part of the New Directors-New Films series in New York last March where it was so well received that it was screened, commercially, in both New York and Los Angeles.
It opens here today at the Rotunda, and if it is humor you want, this film has it. Sometimes it is quite obvious, but most often, it is subtle and delicate. It is Philip Barry (''The Philadelphia Story'') as seen through the eyes of Woody Allen. There is, in fact, an Allen type in the film. He is Charlie, played by Taylor Nichols, and if the name rings no bells, none does in this cast.
That, however, does not mean that these are amateurs. They are not. They have been well chosen by Stillman, who, 20 years ago, was a part of this world, one he describes as ''Manhattan's vanishing debutante scene.'' The film, according to the director-writer, ''chronicles the rise and ultimate decline of a group of young Park Avenue socialites who gather nightly to discuss life, honor and the impending demise of their class.''
The group includes Sally (Dylan Hundley), Charlie (Nichols), Jane (Allison Rutledge-Parisi), Nick (Chistopher Eigeman), Tom (Edward Clements), Cynthia (Isabel Gillies), and Audrey (Carolyn Farina).
Tom is the newcomer in the group. He is standing on a street corner when the others chance by, looking for a cab. They insist he join them, and for a time it looks as though they are slumming, picking up someone from the other side of the city. Tom is, after all, wearing an unfashionable brown coat.
He is not, however, out of the others' class. His parents are divorced, but his father lives in a status high rise in the right section of town.
Everything in this film has to do with the right section. The characters don't always say that, but they don't have to. They are the privileged, born to easy living. Only one works. All the others are home from school for the holidays.
Audrey, the sweetest girl in the group, likes Tom, but he is still stuck on Serena Slocum (Elizabeth Thompson), who has let everyone she knows read Tom's letters to her.
There is, of course, no evidence of street people. Stillman's New York is a time gone by. It is the story of people who were. The director is not ridiculing them. He was, after all, one of them. All he hopes to do is have them amuse us, which they do. Stillman is as good to his characters as Allen is to his. They're funny. He knows that, but he still loves them.
The only reference to the contemporary mood is a mention of mescaline. Otherwise, drugs, like the homeless, are part of another world.
Jack is the funniest of the group. He talks about a friend who tried to talk to sea gulls and was wasting his time because ''Westhampton sea gulls are particularly stupid.''
Tom is funny, too. He doesn't read books. He just reads criticism of the books because that way, you get both the book and an opinion on it, too.
''Metropolitan'' is almost sweet, if you fix it in time. If you do, it is a little like seeing a comedy, a very gentle one, about an alien people on an alien planet.
All in the cast convince, particularly Nichols, Eigeman, Clements and Farina, who may bring Phoebe Cates to mind, and that isn't at all bad.
*** Life among the very young and very rich of a New York City that may no longer exist
CAST: Carolyn Farina, Edward Clements, Christopher Eigeman, Taylor Nichols, Allison Rutledge-Parisi, Dylan Hundley, Isabel Gillies, Will Kempe, Bryan Leder, Elizabeth Thompson.
DIRECTOR: Whit Stillman
RATING: PG-13 (language)
RUNNING TIME: 98 minutes