The printers' and pressmen's unions reached last-minute agreements with The Washington Star yesterday evening, but The Star said the accords occurred so late that it would not publish a New Year's Day edition today.

"I am sorry to say we will not publish [Monday]. We will miss one day, but we will publish the next 364," Star Publisher George W. Hoyt said in a television interview shortly after 11 p.m. Hoyt said The Star would skip today's holiday edition because final agreement with the printers' union "did not come in time."

Time Inc., the publishing company that bought The Star last year, had threatened to shut down the newspaper permanently today unless all 11 unions representing Star employes accepted new, stringently modified five-year labor agreements by last night. The printers' and pressmen's locals were the last of the 11 Star employe unions to move toward contract settlements with the newspaper.

At the end of a dramatic day of court orders, legal battles, bankruptcy warnings and tense bargaining sessions, leaders of the printers' union, which had been embroiled in sharp disputes with the newspaper, announced that they had reached a tentative contract agreement with The Star. The union scheduled a ratification vote on the proposed new contract for 11 a.m. today.

"This is the best possible package we could achieve in this round of negotiations," said William J. Boarman, president of Columbia Typographical Union No. 101, which represents about 175 Star printers. Boarman said he believed his union members would likely ratify the agreement.

The pressmen's union, whose members earlier in the day had voted down a management proposal, reached a tentative accord with The Star yesterday evening. Union members ratified it by a 60-to-29 vote last night.

The Star initially had announced a deadline of noon yesterday for completing new contracts with its employes' unions. The newspaper's agreement to continue bargaining with the printers' and pressmen's unions was announced in a federal courtroom at 6:15 p.m. after a tumultuous day of legal maneuvering.

Shortly after noon yesterday, U.S. District Court Judge Charles R. Richey had granted the printers' union's request for a preliminary injunction to prohibit The Star from carrying out its threat of a shutdown today. In issuing his order, Richey asserted: "The court recognizes the important public interest in Having diverse viewpoints expressed in the media. Rather than see Washington, D.C., become a one-newspaper town, it is everyone's responsibility to do everything possible, within the limits of the law, to keep this paper [The Star] alive."

Richey later "stayed" -- in effect, temporarily withdrew -- his injunction until 3 p.m. today after The Star and the printers' union announced that labor settlements might be completed by then.

As part of the same compromise, The Star did not act on its threat, announced earlier in the day, to file with the court a petition declaring bankruptcy. According to Richey and lawyers participating in the Star dispute, such a bankruptcy filing might have the effect of allowing The Star to abrogate its contracts with the newspaper's employe unions and shut down despite any court injunction -- such as Richey's -- aimed at barring the The Star's closing.

In proposing to file for bankruptcy, Star publisher Hoyt had said in a sworn statement that The Star "has insufficient funds to meet payroll costs and it cannot honor any checks that it might issue commencing January 2, 1979." Star officials have said previous that the newspaper lost $7.2 million during the first 11 months of 1978 and expects to incur a $16 million deficit this year.

Despite the frantic last-ditch labormanagement jockeying, the atmosphere within The Star's Southeast Washington headquarters was described as substantially normal for a holiday weekend.

"There's a little bit of gallows humor but not much of that, either," said Jeremiah O'Leary, a national reporter for The Star. "It is not a deathbed scene by any means. It's a strange 'we've-got-a-paper-to-put-out-so-let's-do-it' scene, although nobody said that."

The day had begun on a gloomy note when Kenneth E. Moffett, deputy director of the Federal Mediation and Conciliation Service and a key mediator in the Star talks, announced that labor and management had remained in disagreement despite allnight bargaining sessions and that The Star had refused either to "stop the clock" or voluntarily extend its negotiating deadline.

The gioom deepened at midday when the pressmen's union -- Newspaper and Graphic Communication Local 6 -- turned down a contract proposal made by The Star's management by a 69-8 vote. The union's leaders had recommended against ratification. One pressman, Jack Jones, described the contract offer as "bad, bad, bad."

But by evening, after the courtroom compromises were announced, the mood among labor and management officials brightened.

Printers' union president Boarman told newsmen that The Star's management had softened its bargaining stance and begun to offer terms that his union's members may accept. "But we won't know for sure until this thing is played out," Boarman said.

At the center of the printers' union's dispute with The Star was a management proposal that initially called for eliminating 80 printing jobs by June and reducing the printing staff to as few as 25 employes during the next five years. Union officials objected to the plan, contending that it meant many union members would be "forced" to leave their jobs and that such compulsory layoffs would violate existing contract guarantees of lifetime jobs for Star printers. Management has proposed to offer "buyouts," amounting to $40,000 each, to any printer who quits.

Last night, Boarman described several key changes in The Star's proposals that led to the tentative agreement on a new contract. He said that although the newspaper still wanted to eliminate 80 printing jobs by June, the retirements "would be voluntary rather than forced." He also said management had offered to guarantee at least 50, rather than 25, printing jobs over the next five years. In addition, Boarman said, The Star had offered higher pay increases than were previously proposed, less severe reductions in special leave time currently granted for printers, and a continuation of the existing contract's provision for lifetime job guarantees for Star printers.

Star officials did not comment on their new proposals to the printers' union yesterday.

A key issue in the bargaining between the pressmen's union, which represents about 85 full-time employes, and The Star's management is "manning" -- the number of pressmen required to operate a press. According to union and other officials, The Star has sought to make significant reductions in "manning" levels.

Officials of the pressmen's union have not disclosed specific "manning" changes included in recent proposals by management. But according to a reliable source, The Star has asserted that its proposed "manning" reductions would not entail any layoffs of regular full-time pressmen. The "manning" cuts may, however, eliminate jobs for substitute, or part-time, pressmen or lead to possible losses in overtime pay, sources say.

After last night's ratification of a new pressmen's union contract, union President Claude C. Hartwick said that although he was "not happy" with the final agreement, it was more acceptable than previous management proposals. Hartwick disclosed few details about the new contract.

None of The Star's existing contracts with its unions had been scheduled to expire before late this year. The newspaper has 14 contracts with 11 unions. The Star's management has sought, nevertheless, to replace all 14 existing agreements with new accords that would give the newspaper broad latitude to make changes in its operations and assure The Star five years of labor stability. Time Inc. has pledged to invest $60 million in the ewspaper during the next five years, previded that the unions agreed to new contracts.

Union officials have said they have repeatedly been told by Star negotiators that The Star is considering the possibility of publishing a morning edition on weekdays.

One other major union -- Local 639 of the International Brotherhood of Teamsters -- reached settlements on two contracts yesterday.

Ronald L. Warren, business representative for Teamsters employes at The Star, announced that members of one Local 639 unit, which includes more than 100 drivers, paper handlers, press cleaners, garage employes and other blue-collar workers, unanimously ratified a new contract at midday. Warren said he had obtained "informal" approval from members of another Teamsters unit, representing about 40 "jumpers," who carry newspapers from delivery trucks to vendors.

Teamsters Local 639 members had previously ratified a third contract covering nearly 300 circulation route managers. Wages had been described as a key issue in the two contracts approved yesterday. Warren said the contract ratified by the drivers' unit provided for increases in wages and fringe benefits amounting to $28 a week in the first year, $29 weekly in the second and $28 in the third. Drivers' current basic earnings, he said, are about $227 a week. CAPTION: Picture 1, Federal mediator Kenneth E. Moffett tells of all-night bargaining session. By John McDonnell -- The Washington Post; Picture 2, Delivery truck returns to The Star plant after Sunday deliveries, bearing advertisement for carriers. By John McDonnell -- The Washington Post