HOW CAN we count the days?

The signs of the times are marked by more than the change of year/day and date in the calendars for 1980. Nature, which once led the list, is still strong this year but is somewhat less evident than art calendars (not calendar art in the old sense of the Marilyn Monroe calendar). Art, usually selected from museum collections and turned into an industry by Universe publishing company (publishers of some 37 calendars), is the strongest leader this year. In general, the quality of the color printing, often from Mondadori, Verona, Italy, is outstanding.

History is coming up strong. Calendars by, for and about women are certainly equal if not superior to most. Though you'd think exercise would've run out of steam, the subject is still in the running. Most of the calendars seem to be close relatives to almanacs, with a great deal of useful information.

The biggest trend continues to be the great proliferation of calendars. There's also a distinct change from the days when calendars were given away. Now you have to pay for them, at no cheap price, but this year there's an extra day in every calendar you buy: It's leap year.

Calendar are on sale at most book stores as well as the museums. The Renwick Gallery and the Corcoran have especially good collections. European art calendars are found at Franz Bader's bookstore in his new location at the corner of 20th and I Streets. UNICEF products can also be bought from the UNICEF information Service and Gift Shop, 110 Maryland Ave. NE. Art

"The Magic Kingdom," the Metropolitan Museum of Art engagement calendar ($4.75) by Stuart Cary Welch, makes me wish for a time machine to swap Iran of today for the Persia shown in the Shah-nameh or Book of Kings from which these minatures are derived. As always, the Metropolitan calendar is first rate, designed by Peter Oldenburg, edited by Sally Fisher and photographed by Walter Yee, printed in Italy.

"Leap Year," ($4.95) a write-on wall calender, was conceived and produced by Robie Rogge, designed by Marleen Adleblum, photographed by Walter Yee and Lynton Gardiner for the Metropolitan Museum of Art. As well as lords a-leaping, the calender includes deer, Greek footracers, French acrobats, Japanese acrobats, a Japanese umbrella jumper, a Leon Bakst costumed Bacchante, American sailors and, of course, the cow jumping over the moon. There are also a series of syncronized leaping photographs for each month.

"American Places, Watercolors, Drawings-Prints," in cooperation with the Corcoran Gallery of Art (Universe, $6.95), is an engagement book with painting celebrating the American landscape -- from Charles Demuth's Art Moderne "Roof Top and Trees" to John Marin's impressionist "Fields and Sky."

"Winslow Homer," in association with the Museum of Fine Arts in Boston (Universe, $5.95), is a wall calendar (14 1/2 by 21 inches open) with 12 watercolors of land and seascapes and the people who make their living outside as interpreted by the great American paiter.

"Japanese Season," in cooperation with the Smithsonian's Freer Gallery of Art (Universe, $8.95), is the most beatiful of the year's art calendars. The calendar is actually a small screen (5 feet by 16 inches open) of 12 panels, reproducing "The Twelve Months," a panel by Katsushika Hokusai (Edo period 1760-1849). The paper is heavy enough to stand alone.

"Art of Our Time," in cooperation with the Albright-Knox Art Gallery in Buffalo, N.Y. (Universe, $3.95), brings us Kenneth Noland's "Wild Indigo" on the cover, Louise Nevelson for November and 11 other contemporary artists. The months are each postcards (the dates detach), so you can send away your past 12 times.

"Chinese Flowers & Birds," in cooperation with the Indianapolis Museum of Art (Universe, $3.95), is another postcard calendar, with a delicate sketch for each month to be sent away to cheer a friend. The calendar part detaches.

"Impressions," in cooperation with the Art Institute of Chicago (Universe, $8.95), is a wall calendar with 12 faithful color prints (15 1/2 by 15 1/2 inches). Among the artists included are Degas, Van Gogh, Monet.

"A Parliament of Owls," by Katharine Tweed (Universe, $4.95), is a wall calendar with places to write. Twelve owl pictures begin with a 19th-century silk "Owl and Lotus Tree" and a strange Hieronymous Bosch picture of an owl that has an apple for a body and human legs.

"Two by Two," in cooperation with the Los Angeles County Museum of Art (Universe, $4.95), portrays two of everything in various art forms -- from Japanese puppies in the snow to "Night Love Scenes."

"A Pride of Cats," by Jean Moss (Universe; $4.95), shows the cat celebrated in the "Cat's Whiskers" by Joan Miro, and a wonderfully decadent cat from 1900 painted by Theophile Alexandre Steinlen.

"The Book of Days," from the National Gallery of Art (Holt, Rhinehart and Winston, printed in Italy, $8.95), includes 73 examples from the collection. The book has only the month and date.

"The Faeries Desk Diary," with illustrations from the Harry N. Abrams, Inc., book of the same name by Brian Froud and Alan Lee (boxed, Peacock Press/Bantam Book Publication, $7.95). Lore and legend with wispy drawings that look as though they were painted under a mushroom.

"Gnomes" wall calendar, with illustrations by Rien Poortvliet, text by Wil Huygen (Harry N. Abrams, Inc., $6.95), includes such useful information as: "The gnome never removes his cap except before going to bed and probably when taking a bath. A gnome without a cap is not a gnome, and he knows it." Photography

"Photography," in cooperation with the International Center of Photography (Universe, $10), is a large (14-by-17-inch) wall calendar with an unusual photograph for every day. Pierre Boogaert's "Synthetization of the Sky," for instance, is quite an achievement.

"The Popular Photography Calendar" (Ziff-Davis, $7.95) is a wide-angle-lens wall day-teller with 12 gorgeous color photographs. Photographic data is in the back.

"The Washington Post Calendar," ($5) photographs by The Post staff, cover photo of the Washington monument by Matthew Lewis, produced by the promotion department, designed by Terry Dale. Shanon Isch wrote the words, including an event a day from the pages of The Post. Typography by Scott Custin, printed by Stephenson, Inc. Nature

"Butterflies," in cooperation with the Smithsonian's Museum of Natural History (Universe, $3.95), is a postcard calendar (remember a friend every new moon). This one has grand pictures by Kjell Sandved.

"The Sierra Club Wilderness," "Trail" and "Wildlfe" calendars; "The Sierra Club Engagement Calendar" and "The Sierra Club Calendar for Young People" are all published by Charles Scribner's Sons, $5.95 each. The full-color nature photographs on heavy paper are magnificently printed in Italy by A. Mondadori. The editors chose the photographs from 30,000 submitted by photographers around the globe.

"The Massachusetts Audubon Society Bird Identification Calendar and Engagement Book, Common Birds of Eastern North America" has 52 drawings and lifestyle information about feathered friends. Illustrations are by John Sill (published by The Stephen Greene Press, P.O. Box 1000, Brattleboro, Vt., 05301, $5.95 for the wall calendar, $7.95 for the engagement book.)

"The Last Wildlands," by the Friends of the Earth (Simon & Schuster, $4.95). The Maine woods are photographed by Joseph E. Holmes to words by Henry David Thoreau."

"The Country Diary Engagement Calendar," by Edith Holden (Holt, Rinehart and Winston, $7.95), is selected from a facsimile reproduction of a 1906 naturalist's diary, "The Country Diary of an Edwardian Lady." This wispy wonder is full of delicate, pastel drawings of birds and flowers and quotations such as: "When April blows his horn/Tis good for both hay and corn."

"The Wake of the Whale Calendar," designed by David Brower (Friends of the Earth/Elsevier-Dutton, $9.95), has eight photographs by Bill Curtsinger of spotted dolphins attending school and whales singing love songs to each other, as well as humpback whales and other marine mammals of the deep. t

"The Sea 1980," by Eric and Linda Booth Schweikardt (Methuen, $7.95), has pleasant enough photographs (by Eric), but the quotations selected by Linda Booth (no relation) are the reason to buy this book. "Who goes to sea for pleasure, would go to Hell for a pastime." Religion

"The Illustrated Jewish Desk Calendar," designed by Jack Jaget, was printed in Israel (boxed, Holt, Rinehart and Winston, $8.95). The book is full of illuminated manuscripts. But the admonitions glitter with a brilliance and a cutting edge as bright and sharp as a rapier: "To shame a man in public is like shedding his blood."

"The Psalms Engagement Calendar" has calligraphy by Emil Antonucci, with psalms excerpted from the Jerusalem Bible for each week (Paulist Press, $6.95). Women's Way

"The Woman's Calendar," by Jurate Kazickas and Lynn Sherr (Universe, $4.95), is an engagement book so full of information you may forget what it was you wanted to write in it. Lest we forget there's sexist pig sayings: "For me, women are only amusing, a hobby. No one spends too much time on a hobby." m-- Henry Kissinger.

"The Whole Woman Calendar," by Meryl Natchez and Maureen Solomon (Foolproof Press, POB 647,Berkeley, Calif. 94701, $4.95), has women like Sarah Caldwell, director of the Opera Co. of Boston, who says, "The secret of living is to find people who will pay you to do what you would pay to do if you had the money."

"The 365 Women a Year Calendar," (Workman Publishing Co., $4.95). Aug. 4: "Too much of a good thing can be wonderful." -- Mae West, film actress. Words

"Puzzling Through 1980 With Margaret Farrar and Company" is a crossword calendar with a puzzle a week -- they look as though they'd take a week to work (Fireside Book by Simon and Schuster, $4.95). If you have to cheat, the answers are in the back.

"The Kahlil Gibran Diary" (Alfred A. Knopf, $5.95) "Work is love made visible," and similar thought, one per week. Like the crossword puzzle, it would take you a week to puzzle out Gibran's quotations.

"The Calligrapher's Quote Calendar," a wall calendar by Margaret Shepherd (Collier Books, $4.95), gives a fanciful example a day of a quotation caligraphed ("Why should I feel lonely? Is not our planet in the milky way?" -- Henry David Thoreau).

"Calligraphers Engagement Calendar: Quotes from Shakespeare," edited by Paul Freeman (Pentalic Book by Taplinger Publishing Co., $8.95), is for people who don't really want to know what the quotation says.

"The Page-A-Day Wall Calendar" (Workman Publishing Co., $4.95) gives you a word, its prononuciation and definition to think about every day. Jan. 1 with "auspicious, adj. 1. promising" is fine, but what of Jan. 4 with "macerate, v.t. 1. to soften, separate or decompose by steeping in a liquid."

"ythe 365 Jokes, Puns & Riddles Wall Calendar , Ha! Ha!" (Workman Publishing Co., $4.95) Jan. 6: "Then there was the guy who was so mean that when he was in the hospital, the only get-well cards he got were from his nurses." Exercise

"Sailing," with 12 photographs by Eric Schweikardt (Universe, $10), is a large 15 1/2-by-21 1/2-inch) write-on wall calendar picturing boats such as the Tenacious and Acadia.

"Skiing," with 13 photographs of snowy moments by Eric Schweikardt, is also a write-on wall calendar (Universe, $5.95).

"The Runner's Calendar," with a text by Dr. George Sheehan (Simon and Schuster, $4.95), has a text so sugary you might gain weight reading it. All the pictures show really unattractive males looking exhausted except for one fine picture by J. C. Dewolf (Paris Match) showing a man running along with his butler (black tie, black morning suit with vest) following close behind with a bottle of Perrier water and a glass.

"The Dieter's Guide to Weight Loss During Sex Desk Diary," by Richard Smith (Workman Publishing Co., $4.95), can hardly be quoted in a family newspaper. But I can say it lists "intensive flirting (winking with eyes)" as burning 10 calories.

"The Arnold's Schwarzenegger Calendar With Exercises" (Simon & Schuster, $4.95). The end of sexism is at hand. Now we have pin-up boys. Gardening

"The Botanical Calendar," in cooperation with the New York Botanical Garden, is an engagement calendar (Universe, $6.95) with an interesting text by George Bookman, vice president of the New York Botanical Society and illustrations from Flora Monacensis by Franz von Paula von Schrank, published in Munich between 1811 and 1818. The line drawings are by John Burton Brimer.

"Crockett's Victory Garden Calendar," by Jim Crockett, is a wall calendar with handsome flower pictures by Russell Morash (Little, Brown and Co., $6.95). Useful information on flowers of the field and the house including cautionary notes for each month's planting. Comes with a packet of impatien seeds, mixed colors. About the House

"Architectural Digest Engagements," with photographs from the magazine (Holt, Rinehart & Winston, $20), is the best-looking (and it should be at that price) diary I've seen this year. Luxurious color pictures start each month, inviting us into a world of how we'd like to live. Each month begins as well with lists of antique shows, art events, superbowl in Pasadena, Ocktoberfest in Munich.

"Bon Appetit Social Planner," with menus and recipes and photographs from the magazine (Holt, Rinehart and Winston, $14.95), is a lush book with useful pages to list your menus (or events) of the day. There are 13 or so pages in back to list the data on your largest parties for tax references. Well worth the price (tax deductible?).

"The Antiques Engagement Calendar" (Mayflower Books, a Main Street Press Calendar, $6.95) has, besides 53 handsome pictures, a list of antique shows for the year.

"The Food Calendar," with 12 luscious exotic delicacies photographed by John Paul Endress (Universe, $5.95), is a wall calendar with recipes for each month. I could certainly eat Thai beef salad every day of July. Children

"The Magical World of Children," by UNICEF ($4.95), is an engagement calendar in English, French and Spanish with lyrics and music of children's songs in the language from which they come.

"The UNICEF Wall Calender, ($1.50) with children's art from 13 countries, has a great list of national and religious holidays including Lazy Bones Day in the Netherlands and Hooting at Hunger Day in Ghana.

"The Smithsonian Engagement Calendar: A Child's World" (Universe, $5.95). Delightful representation of children are found in many places in the Smithsonian's museums. A Kate Greenaway sketch is embroidered on a 1880 silk crazy patchwork slumber throw. A World War I poster shows a blond darling with the caption "My Daddy Bought Me a Government Bond of the Third Liberty Loan. Did Yours?

"The MacMillan Children's Calendar," by Jean and Roy Doty (MacMillan, $3.95), is full of useful information: "Because water clocks froze in cold weather, a French monk, in the eighth century, used sand instead of water and invented the hourglass." The Performing Arts

"Movie Romance Calendar" (Doubleday, $4.95) is a wall calendar designed by Dick Umnitz with captions and movie quiz by Cathy Camhy. For those of us of another era, this calendar offers the Male Pinups -- Leslie Howard as Romeo, Ronald Coleman as Charles Rainier in Random Harvest. That's the way men should look. Weep your heart out, Arnold Schwarzenegger.

"Dancing Times," an engagement calendar by Nancy Reynolds (Universe, $5.95), has a diverse sampling of great dance moments, including Fred Astaire in "Top Hat."

"Theater Arts," from the Collection of the Museum of Modern Art by William S. Lieberman (published by MOMA, $7.95), is a sumptuous wall calendar made up from a little-known and fascinating collection. The cover alone, Leon Bakst "The Firebird, 1913," is worth the price.

"On Stage," in cooperation with the Theatre Collection, Museum of the City of New York (Universe, $3.95), a postcard calendar (write a note a month) with illustrations from the "Playbills" of the 1920s. History

"Inside America," in cooperation with the National Trust for Historic Preservation (Universe, $5.95). This desk calendar has a fine collection of interiors, almost impossible to duplicate today, preserved from other times and places. Some of the most marvelous are from Washington.

"The Calendar History of Alexandria, Arlington Co. & Fairfax Co." by Paul S. Worboys (7413 Parkwood Court, Apt. 302, Falls Church, Va. 22042). Sketches and information for these jurisdictions are put together in a wall calendar. Twelve historic sites and notes for every day.

"Postals of Maryland's Past," by M. E. Warren (P.O. Box 1508, 1935 Old Annapolis Blvd., Annapolis, Md. 21404, $4.95), is made up of old postcards showing Maryland scenes with history notes on the days. Diversities

"The Gay Engagement Calendar," compiled by Martin Greif (Mayflower Books, $5.95), carries a disclaimer that it includes "the names of both gay and straight people . . . their inclusion in this calendar is in no way to be construed as an implication that they themselves are homosexuals." After that, it goes on to show a number of striking photographs with explicit comments on various celebrities' taste in pleasure.