"More or less," said Samuel Schoenoaum of the University of Maryland, who should know the answer if anyone does.

Someone had asked the distinguished author of "William Shakespeare: A Documentary Biography" whether April 23 was actually the Bard's birthday, and in true scholarly fashion he hedges his answer. "He was entered in the parish register at Stratford on April 26, 1564," said Schoenbaum, "so that we can assume he was born on or about April 23. He died on April 23, 1616, so that would give his life a nice symmetry."

Whether it was a brithday or an unbirthday, the Fogler Shakespeare Library made much ado about something yesterday, and the evening climaxed with 208 guests (who had paid $50 per ticket) standing, in the library's exhibition hall and singing, "Happy birthday, dear William."

Earlier, in the tiny theater which is a replica of Shakespeare's Globe, son recitation of "Happy Birthday, william shakespeare," under the leadership of the Fogler's director, O.B. Hardison, before the members of the Fogler Consort and the Fogler Theatre Group presented music related to Shakespeare and readings from his plays and poems.

On their way into the theatre, guests were given glasses of champagne to toast the Bard. Afterward, there was a buffet, more champagne and dancing in the great exhibition hall-a replica of a Tudor/Stuart great hall with heraldic banners hanging down from the high ceiling bearing th coats of arms of members of the Elizabethan nobility.

Portraits of Shakespeare looked-not disapprovingly-from the walls as the revelry mounted. There was a look of distress on the face of King Lear in one portrait, but there always is.

"What's a nice fellow like you doing in a place like this?" one guest asked an impassive , white bust of the poet, putting an arm around his shoulder and offering him a glass of champagne. The poet's eye, in a fine frenzy rolling, seemed to be looking at the ceiling, where more than two dozen pink and white gas ballons were nestled, far out of reach and with no place to go.

"I suppose they'll come down eventually," said a member of the Fogler staff. The rest of the balloons were clustered at the two entrances to the room, taped to the floor, and guests who wanted them took them-sometimes setting one free as they captured another.

The centerpiece of the main buffet table was a handsome replica of the Globe, and there was a massive birthday cake (Tudor-style with shafts of icing that looked like half-timbers embedded in icing that looked like plaster). There was only one candle on the cake, but an icing inscription bore the Roman numerals CDXV, indicating that it was a 415th birthday.

But it was not all balloons and champagne. Each of th guests was given a scroll with Shakespeare's 17th sonnet ("Shall I compare thee to a summer's day?") printed in Elizabethan calligraph, the Devron orchestra played "Brush Up Your Shakespeare" and the program in the theater presented a broad spectrum of the poet's art, from a delicately bawdy reading of passages from "The Passionate Pilgrim" to a searing scene from "Julius Caesar" in which Brutus and Cassius have a falling-out.

The musical program included a lovely, witless song about a cuckoo, four settings of Shakespeare by Purcell and Arne sung with good style and rich tone by tenor Michael Hume, and a witty 17th-century song by another Hume, Tobias, comparing tobacco to love.

The party was the climax of a busy day's activity, which included an 18-hour fund-raising Shakespeare festival broadcast on WGMS-FM, with a whole catalogue of items offered for sale to help with the Folger's $6.7 million construction fund. The premiums ranged from a "Shakespeare Is the One" button for $1 and a T-shirt bearing a quotation from "The Winter's Tale" ("Jog on, jog on") for $6, up to concert of folk music by a group called The Irish Breakdown for which the minimum bid was $1,000. Notable prizes included props and costumes from Folger Shakespeare productions-two thrones fo r "Richard II," a Hamlet suit (size 38) and Prospero's cape from "The Tempest" ("suitable for street wear," said the catalogue) for only $200.

Whether it was exactly the Bard's birthday or not, it was a good day for a party that could be heard, at its climax, more than a block away. It was also a who can claim it with more solid documentation than Shakespeare include Shirley Temple, Vladimir, Nabokov, J.P. Donleavy and Sergei Prokofiev. Perhaps somewhere in Liningrad last nigh there was a party where people sang "s dnyom rozhdeniya a sergi Sergeievich but the celebration could hardly only have been more lusty than the onefor Shakespeare. CAPTION: Picture, The Folger Consort and soloist Ann Monoyios; by Margaret Thomas