More by accident than by grand design, January looks to be one of the most extraordinary months ever in public television, decorated as it is by the premieres of such auspicious and viewable projects as, last week, "Creativity" with Bill Moyers and -- tonight on Channel 26 -- the premieres of "Life on Earth" (at 8) and "American Playhouse" (at 9).

"Life on Earth" is a magnificently photographed nature series imported from the BBC (and co-produced by Warner Bros. here), a lavishly illustrated picture book on the checkered and polka-dotted history of this planet. "American Playhouse" is a long overdue but unquestionably welcome new anthology that PBS justifiably calls "the most ambitious drama series in public television history."

Sadly, this little renaissance comes at a time when public television is facing financial famine at the hands of the Reagan administration and its cruel, reckless, potentially ruinous budget cuts.

David Attenborough, the zoologist and anthropologist who conducts the historical tour of "Life on Earth," follows in the footsteps of such urbane public TV interlocutors as Jacob Bronowski with "Ascent of Man" and Carl Sagan with "Cosmos." Attenborough is an affable and unpretentious guide who is willing to ride a donkey down into the Grand Canyon or scuba dive off Australia's Great Barrier Reef in pursuit of fossil proof about animal origins; his way with words is unaffected clarity, as when he casually describes the Medusa who gave her name to a spiny fish as "the unfortunate lady in the Greek myth who had snakes on her head for hair."

Unfortunately, Attenborough occasionally gets caught in the gee-whiz trap that so often ensnared star-struck astronomer Sagan (though Attenborough is hardly so gee-whizzy in his delivery). Where Sagan was forever marveling at the "billions and billions of years" since this or that star first twinkled, Attenborough is repeatedly noting the ages of fossils in hundreds of millions of years or so.

After some exposure to this, it becomes not terribly enthralling to learn that the dragonfly first fluttered 300 million years ago whereas the horseshoe crab first crawled 500 million years ago -- though in the later case, Attenborough confesses that no one really knows "for sure." Well when you get right down to it, anything over a million years is pretty unfathomable anyway; maybe anything over 40 years is.

"These immense periods of time baffle the imagination," Attenborough confesses; he tries putting it all into a perspective similar to Sagan's universal calendar, with the history of the planet reduced to a single year and each day representing 10 million years. Here we go again. But the pictures are often spellbinding, whether of a mama crocodile with her baby peeking out from between her teeth, or of the balletic undulations of a luminescent jellyfish. "Life on Earth" can be as marvelous and magical as life on earth.

Life in John Cheever's fictitious bedroom suburb of Shady Hill can be fairly marvelous, too, and though Cheever seems by no means to have mastered the craft of television playwriting, his "Shady Hill Kidnaping," first of the "American Playhouse" series, makes for a wickedly witty hour, and the production, taped in and around Hartford, Conn., is as bright and shiny as the stainless steel in a hospital emergency room.

Cheever unwisely chose as the pretext for this acerbic social comedy about upper-middle-class folly the abduction, or the imagined abduction, of a 5-year-old boy named Toby. This is a premise that not everyone will be comfortable with, and Cheever isn't too comfortable with it either.

In addition, his dialogue is often unwieldy and overly literary, so that the actors -- like George Grizzard as Toby's grandfather and the wonderful Polly Holliday as grandma -- sometimes appear to be wrestling it to the ground rather than speaking it. And yet even unplayable plays can be captivating if they are by sufficiently gifted writers. By any standard, we would probably have to rank Cheever as sufficiently gifted.

Holliday is particularly fine as Grizzard's peeved and distracted wife, who sits behind a newspaper at the breakfast table and sputters at her husband, "I can tell by the way you're chewing your toast that you're going to fight with me because I didn't scramble you some eggs." The scene is a delightful flesh-and-blood translation of a New Yorker cartoon. Eventually she watches in dismay as workmen tear up the back lawn; it seems the bank won't loan money to pay ransom notes, but they are eager to advance the cash for a new swimming pool.

At fairly regular intervals, Cheever interrupts the narrative for mock commercials starring Celeste Holm as "The Celebrity," a winsome member of the ersatz glamorati who is hawking a brew called Elixircol, "the true juice of youth." It's a cure for such suburban maladies and miscellaneous malaises as not finding your name mentioned in the social column, but, as we learn later, it has its limitations.

By the end of the hour, some of the Cheever mannerisms that had been rather irritating grow strangely endearing. The entire community of Shady Hill has turned the search for Toby into a self-aggrandizing civic event, with no less a rarefied commodity than "federal monies" involved (ironically or not, considering this is public TV and grandpa's son wears a Channel 13 T-shirt). There is a parade, and a homecoming, and Cheever's three-martini voice on the soundtrack, and, oddly enough, what had been merely droll becomes moving.

"Shady Hill Kidnaping" was produced by Ann Blumenthal and directed with effortless fluency by TV veteran Paul Bogart. The music, ideally delicate and wry, is by Jonathan Tunick. If one of the purposes of "American Playhouse" is to lift one's spirits and tickle one's fancy, the series is off to a fine and fancy and ticklish start.

Future programs will include "Who Am I This Time?," adapted from a Kurt Vonnegut story and starring Christopher Walken and Susan Sarandon; a TV adaptation of the off-Broadway hit "For Colored Girls Who Have Considered Suicide/When the Rainbow is Enuf"; a seven-part docu-drama about Jay Robert Oppenheimer; and "Weekend," the first original teleplay to be written by novelist and short story writer Ann Beattie. Within the context of the current TV season -- in fact within almost any context you can shake a stick at -- "American Playhouse" could turn out to be television Shangri-La.