To William Chase, every day is a holiday. Literally. If its not Be Late for Something Day (Sept. 5).it's National Cheer Up the Sad and Lonely Day (July 11). Or National Ding-a-Ling Day (Dec. 12). Last Tuesday was Be Kind to Your Astrologer Day, and there's Foodservice Distributor Salesman's Day, on Sept. 22. "I like the idea of celebrating," says Chase. No kidding.

By day William Chase is the (not necessarily) mild-mannered chief librarian for the Flint Journal in Flint, Mich. By night he turns into the hard-driving editor and publisher of Chase's Calendar of Annual Events, a slightly staggering compendium of 2,500 special occasions scheduled for observance or commemoration.

Under Chase's benevolent gaze, no day, however humble has gone unrewarded. Each of the 365 has at least three observances listed, with the 31 events of May 31 topping the list. And Chase does not stop with merely listing days or weeks (Tableware, March 27-April 1) or even months (Naitonal Havasalad, Aug. 1-31). Foreign celebrations, like Up Helly AA', very big in Lerwick, Scotland, on Jan. 31, and the Our Lady of Girsterklaus Procession, more or less a tradition in Luxembourg since 1328, are given their due, and so are various American festivals. The World Cow Chip Throwing Championship, for instance, begins April 19 in Beaver, Okla., while the International Chicken Flying Meet starts in Rio Grande, Ohio, a month later, with the august Pennsylavia Bed-Making Championship not beginning in Philadelphia until the 21st of September. There is even a Weeks' Week to celebrate all the celebrating and a National Nothing Day to rebel against it.

Before he turned to the annual events business, Chase's main claim to fame was a desire to open a book-store devoted exclusively to the works of George Bernard Shaw. The following letter from the great man put an end to that: "You cannot run a bookshop on the work of a single author, especially one whose name repels so many customers. You are evidently not a born bookseller. Try selling hot dogs".

Instead of hot dogs, Chase in 1957 turned to calenders because the editors of his newspaper, like editors everywhere, were constantly coming to him with a lot of questions like "what's an idea for a feature story, what's happening next week, is there really a National Peanut Week?" (No, its's a month and begins March 1). His listing earned the sanction of the Chamber of Commerce, which had taken over the chore after the U.S. Department of Commerce gave up on it, and has sold a third of a million copies in the 21 years of its existence.

And though members of the general public are encouraged to send $7.95 to Apple Tree Press, Box 1012, Flint, Mich. 48501, and get 80-page calendars for themselves, most of the recipients are still media people hungry for stories as well as, curiously enough, nursing home folks who think its cheery to serve oldsters lentils during National Lentils for Lent days or gazpacho during Gazpacho Aficionado Time.

Absolutely anyone who wants can write to Chase and request a day if he or she has a reasonable reason for wanting one. There is no limit to the number you can request - Pickle Packers International, for example, has received sanction for Party Time Is Pickle Time, International Pickle Week, Snack-a-Pickle Time, National Pickled Pepper Week and even Holidays Are Pickle Days - and Chase has a definite weakness for what he calls "the lighter side of celebrations."

"We try not to be hard-nosed about this," he says, thinking perhaps of National Fink Day or National Aardvark Week. "People enjoy celebrating for a lot of different reasons, and if something sounds like fun, like something people would enjoy knowing about, we are quite generous in our selections."

Decidedly more serious are days dubbed special by presidential proclamation - Save Your Vision Week, beginning on March 5, and National Poison Prevention Week, beginning March 19, for example - which are marked by great black dots in Chase's calendar. The first one was Thanks-giving, proclaimed by George Washington in 1789, a day that came into being the same way presidential days still do: Both houses of Congress ask the president nicely to do it and, not wanting to get everyone in Congress mad at him, he agrees.

To insure that nothing unworthy of the nation gets put on the president's desk, some fearfully stiff criteria have to be met. In the House of Representatives, a majority of the members.

Furthermore, according to the official policy of the House Committee on Post Office and Civil Service, which somehow got charge of what it calls "commemorative legislation," no days can be set aside for commercial enterprises, specific products, fraternal, political or sectarian organizations, particular states, cities, towns, counties or schools, nor for any living persons. The idea, obviously, is to get proposals simply bursting with "national appeal and significance."

The flaw in this smooth-running machine is that the president, being president, can decide to make a day a Day all by himself, perhaps because someone on his staff has unknowingly made a commitment, or just because he gets up and feels like it. President Carter, for instance, has on his own declared International Clergy Week, Black Press Day, U.S. Space Observance Day and World Law Day since taking office. While there is nothing wrong with any of these days, other groups who feel equally worthy but are told everything must go through Congress tend to get miffed when word of the exceptions leak out.

Also miffed by all these days was former representative Ken Hechler, who declared on the House floor back in 1973 that National Next-Door Neighbor Day made nobody more neighborly and that Clean Water Week brought us no cleaner water. Hechler said such days were a terrible waste of lawmakers' time, but they continue to proliferate and Hechler isn't even a congressman any more.

Back in Michigan, William Chase looks at days from a somewhat different perspective. "I think people are looking for things to celebrate," he says. "In a world in which we have become somewhat depersonalized, with all these numbers, there's a need to release some of that anxiety, so people tend to enjoy the lighter side of celebrating."

And with all 2,500 celebrations to choose from, what is Chase's favorite day? "Ihave a rule, I never tell anybody what my favorites are," he says. "I just say, 'Whatever's on today'".