PERSISTENT QUESTION ABOUT DISCREPANCIES ON HART BACKGROUND

Senator Gary Hart's candidacy for the Democratic Presidential nomination continues to be dogged by a number of questions about his personal background.

These questions deal with subjects ranging from changes in his birthdate to adjustments in his official biography. Many of them have been widely discussed in political circles, and Mr. Hart has addressed them at various times.

Today, for example, The Associated Press quoted him as saying in an interview that he had discussed ''over and over again in great detail everything there is about everyone'' of the questions raised.

''What I find is a suspicion of my word which really bothers me a lot,'' the Colorado Democrat said in the interview. ''When I tell the truth, I expect my word to be taken as truth. Obviously, if I don't tell the truth and people can prove it, that's a very disastrous thing.''

Persistent Questions

No one has proved that Mr. Hart is not telling the truth. But the questions persist because some of the answers given by Mr. Hart contain discrepancies. What follows is an examination of the questions that have been raised.

Senator Hart, who has emerged with former Vice President Walter F. Mondale as one of two leading Democratic contenders, has changed his signature dramatically in the last decade and has listed his age incorrectly for nearly two decades,

Despite his reducing his age by a year, Senator Hart was still too old for the Naval Reserve commission he obtained in late 1980 and required a special waiver of age regulations before being sworn in with a commission in the Navy Judge Advocate General's Corps.

Moreover, a survey of his vital statistics discloses, he has slightly inflated an item on his official Senate biography in the Congressional Directory and over the years has dropped references to his days as national campaign director for the 1972 Presidential campaign of Senator George McGovern. Discrepancies on Birthdate

Mr. Hart now acknowledges that he was born on Nov. 28, 1936, which makes him 47 years old. In his official biographical listing in the Congressional Directory and in several legal documents, including his Colorado driving license and his applications to the Virginia State Bar and the Colorado Bar Association, Mr. Hart listed his birth date as Nov. 28, 1937, which would make him 46 years old.

At the same time, Mr. Hart has not consistently listed 1937 as the year in which he was born. The earliest known instance of Mr. Hart's using the incorrect birth year is his application to the Virginia Bar, where he was admitted on Feb. 19, 1965. However, in his official declaration of his candidacy for the Senate in 1974, now on file in the Colorado State Archives, Mr. Hart listed the correct year of birth.

Such discrepancies can be found in a number of legal or official documents Mr. Hart has filed over the years. He listed his incorrect date of birth in 1967, when he filled out a biographical questionnaire as part of his application to the Colorado Bar Association, but an onionskin resume attached in 1969 to a standard inquiry by the National Conference of Bar Examiners includes the correct date of birth. Hart Minimizes Question

In recent interviews Mr. Hart has minimized the importance of the different birth years. ''I can't account for every piece of paper that's been written by my campaign or anyone else, but I have never disputed - I can't recall disputing what my correct age is,'' he said late last month on the CBS News program ''Face the Nation.''

However, Mr. Hart has also attributed the differing birth years to a family joke about the relative ages of his mother and her siblings. He has said that the use of an earlier birth date can be attributed to a family effort to make his mother appear younger than she really was, an explanation that has been challenged by his uncle, Ralph Hartpence.

''Dates on some biographical documents reflect human error or inadvertency undoubtedly produced by longstanding, but lighthearted, family debates over the relative ages of family members,'' Mr. Hart said the other day. ''Clearly there is no issue of personal profit or political gain involved in this matter.'' Name Changed in 1961

Mr. Hart was born Gary Warren Hartpence and changed his name to Gary Warren Hart in 1961. Early in the Presidential campaign the candidate said his parents had sought the change in the family name to Hart to return to what he said was the original family name. He now says that the change to Hart grew out of a joint decision with his parents. His uncle said in an interview that he believed a possible political career was one of the motivations prompting Mr. Hart to simplify his surname.

The Colorado Democrat has said that Hart was the family's original name in Ireland, but a Washington genealogist, apparently acting on his own, who has done research in the forebears of the Presidential candidates, said that the family's original name was Pence.

''The records I have seen show there was no Hart in his background,'' said the genealogist, William Addams Reitwiesner, ''Mr. Hart is not a genealogist, and this type of confusion is perfectly normal.''

Despite the change in how he listed his age, Mr. Hart required a waiver of age restrictions from a former Secretary of the Navy, Edward Hidalgo, when he requested a commission in the Navy Reserve. Reserve Commission Sought

Mr. Hart has said he first sought a Naval Reserve commission in the late 1970's because of the turmoil in the Middle East and the possibility of the United States' going to war over oil reserves in the area.

''He felt he should have a personal stake in votes he might cast on sending young men the age of his son to die in the Middle East,'' said Beth Smith, Mr. Hart's Senate press secretary.

Lieut. Thomas A. Yeager, a Navy spokesman, said Mr. Hart's classification was stand-by reserve (active), a category used for key Federal employees ''so the United States isn't drained dry'' in times of war. According to the Navy, this category would not be called up immediately in the event of a mobilization. Mr. Hidalgo said that Senator Hart approached him about a commission several years ago. ''He didn't give me any particular reason, nor did he have to,'' he said. ''I was very happy to have a Senator to be sworn in. We're always happy to have qualified people in the Navy.'' Discussion of Naval Rank

Mr. Hidalgo, now a Washington lawyer, said that he had conferred with Rear Adm. John S. Jenkins, then the Judge Advocate General of the Navy. Mr. Jenkins, who is now retired from the Navy and is working as assistant dean of the George Washington University Law School, said that he had advised that Senator Hart be commissioned a lieutenant (j.g.).

''He didn't bring to the program anything that was so unusual that we could recommend appointment at a higher grade,'' Mr. Jenkins said.

However, a senior Pentagon official who was aware of the circumstances and spoke on condition that he not be identified, said that Mr Hart's staff had sought to win him a commission at a higher rank because, as the official recalled, ''his contemporaries in Congress who served in World War II or the Korean War had equivalent ranks.''

Kathy Bushkin, Mr. Hart's press secretary, said that Mr. Hart was urged by Capt. John S. McCain, then the naval Congressional liaison officer, to seek a high rank because he was a member of the Senate. Advice From Liaison Officer

Mr. McCain, who is retired from the Navy and is now a Republican member of the House of Representatives from Arizona, said that he did not urge Mr. Hart to seek any particular rank based on his status as a member of Congress. ''I did say that, in keeping with his age, the rank of lieutenant commander or commander was appropriate,'' Representative McCain said.

The senior Pentagon official said that the Navy did not check the birthdate that Mr. Hart provided, which was incorrect, against his birth certificate. ''When a United States Senator fills out a form,'' he said, ''it's not like Johnny Jones walking into a recruiting station.''

Mr. Hart, who receives no pay or benefits from his reserve status, served for 10 days of active duty with the Sixth Fleet in the Mediterranean in August 1981. He was promoted to lieutenant on Jan. 1, 1982, based on his time in the service.

Although some of his critics on Capitol Hill have asserted that Senator Hart sought the commission so as to add military service to his resume, he does not list it in his biography nor does he include it in campaign literature. Work at Interior Department

In his Senate biography, Mr. Hart lists being a ''special assistant'' to Secretary of the Interior Stewart K. Udall in the mid-1960's. Department records, however, list Mr. Hart, then a young lawyer, as an assistant in the office of the department's solicitor, though Mr. Udall remembers working with Mr. Hart on a number of projects.

Frank J. Barry, who was the Solicitor of the department at the time, recalls Mr. Hart as ''extremely able and dedicated'' but said in a telephone interview that Mr. Hart had worked directly for him.

Mr. Udall said he had a ''clear recollection'' of those years. ''My solicitor hired a team of young lawyers to be troubleshooters, to work on major new problems,'' Mr. Udall said. ''They were, from the standpoint of budget, working for him in the Solicitor's office. Most of them worked directly with me and with the Solicitor.''

Mr. Udall added in a reference to Mr. Hart: ''Politicians put a little gloss on things, and maybe this is an instance of that, but it's not very much gloss. Any number of people know that he worked directly with me several important matters.'' Changes in Biographical Listing

When Mr. Hart first joined the Senate, his biographical listing in the Congressional Directory did not mention his degree from the Yale Divinity School but included references to his work as a volunteer in the Presidential campaigns of John F. Kennedy and Robert F. Kennedy and his work as national campaign director for Mr. McGovern.

A reference to his divinity school degree appeared the next year, but the references to the two Kennedy campaigns did not. By 1981, the reference to Mr. McGovern had disappeared from the listing in the Congressional Directory, although a biography being distributed by his campaign office does note that he directed Mr. McGovern's 1972 campaign.

''Years after being a Senator he was still being introduced by people as George McGovern's campaign manager,'' said Mrs. Bushkin, explaining why Senator Hart requested that the reference be removed.

''It was a reaction to that,'' she said. ''We weren't trying to hide it.''

His biography in the Congressional Directory lists him as having taken his undergraduate degree from ''Bethany College, Bethany, Okla.'' There is a Bethany College in West Virginia, but the institution in Oklahoma is known officially as Bethany Nazarene College and it is affiliated with the Church of the Nazarene, a conservative Protestant denomination. Signature Is Altered

Since coming to the Senate in 1975, r. Hart also has made adjustments in his signature, changing from a cursive signature that included his middle initial to a modernistic, printed signature, almost digital in its appearance, without a middle initial.

''He got many complaints, including an editorial in a newspaper in Colorado, that people couldn't read his signature,'' said Miss Smith, Mr. Hart's Senate spokesman. ''He changed his cursive signature to a printed one that could be clearly read.''