B.C./A.D. or B.C.E./C.E.?

My claim to fame? responsibility for the first mistake made by an earthling on an extraterrestrial body.

As a White House speech writer, I had a hand in writing the text on the plaque marking the spot where Apollo 11 astronauts first set foot on the moon. To slip in an unobtrusive reference to God, I wrote, ''July 1969 A.D.'' When some alien from a U.F.O. lands there in a few thousand years, it will surely know that the initials stand for the Latin Anno Domini and get the point that our first explorers feared only God.

My mistake was putting the A.D. after the date. Correct dating usage is to put B.C., ''before Christ,'' after the year and A.D., ''in the year of our Lord,'' before the year.

I may have goofed in more ways than one. In a recent column about what to call the Bible, I posed the question: Should it be B.C. or -- in deference to Muslims, Jews and other non-Christians -- B.C.E., standing for ''before the Common Era''? In the same ecumenical way, the question arises: should A.D. or C.E., ''Common Era,'' be used to signify the time since Jesus of Nazareth was born (in 4 B.C., for reasons of calendar error; it is not in my linguistic purview to explain)?

What a mail pull. From Prof. Harold Bloom of Yale, my Bronx Science classmate whose landmark book ''The Western Canon'' booms across the Kulturkampf battlefields: ''Every scholar I know uses B.C.E. and shuns A.D.''

The shunning of A.D. (like the one that sits wrongly placed on the moon) goes clear up to the Supreme Court. Adena K. Berkowitz, who has both a law degree and a doctorate in Hebrew literature, applied to practice before the Court. ''In the application,'' she wrote, ''I was asked if I wished 'in the year of our Lord' to be included as part of the date listed on the certificate or omitted.'' She chose to omit: ''Given the multicultural society that we live in, the traditional Jewish designations -- B.C.E. and C.E. -- cast a wider net of inclusion, if I may be so politically correct.''

That application form reflects a new sensitivity in Washington; a Court spokesman said that the choice is only 11 months old. By nearly 2 to 1, other scholars and some members of the clergy agreed with Bloom and Berkowitz. ''Christians could be a little less triumphal,'' noted the Rev. Charles B. Atcheson, rector of All Saints Church in Waterloo, Belgium. ''Yes, the world has largely accepted the Christian calendar scheme that begins, a little inaccurately, with the birth of Jesus, but calling it 'the common era' is not a great loss and could be taken as a sign of acceptance of others. It will not be lost on anyone what happened shortly before the year 1.''

Disagreement is sharp. ''It is one thing to deny the divinity of Christ,'' observed Michael McGonnigal of Silver Spring, Md. ''It is quite another to deny His historical existence, which is what is implied by the superfluous switch from the traditional B.C. to the P.C. B.C.E.''

David Steinberg of Alexandria, Va., called B.C.E. ''a strained innovation requiring explanation in most of America.'' and James McInerney Jr. of Cleveland Heights, Ohio, said, ''That this dating system has become accepted worldwide reflects the cultural importance of Christianity in world history.''

A Muslim view from Khosrow Foroughi of Cranbury, N.J.: ''Jews and Muslims have their own calendars. Muslims have a lunar calendar reckoned from A.D. 622, the day after the Hegira, or flight of the Prophet Mohammed from Mecca to Medina. The Jewish calendar is also a lunar one and is the official calendar of the State of Israel. $(this year is 5757.$) The Christian or Gregorian calendar has become the second calendar in most non-Christian countries, and as this is the Christian calendar, I cannot see why 'before Christ' and 'in the year of our Lord' would be objectionable.'' Contrariwise, a leading student of Islam, John Esposito of Georgetown, said, '' 'Before the Common Era' is always more acceptable.''

I turned to Hershel Shanks, editor of the Biblical Archeology Review, who helped break the scholarly monopoly on the Dead Sea Scrolls. Two years ago, his journal put out a delightful paperback -- ''Cancel My Subscription!'' -- with a section of letters on this controversy. As a result, the magazine let authors have their individual choice and published a careful note on style: ''B.C.E. (before the Common Era) and C.E. (Common Era), used by some of our authors, are the alternative designations for B.C. and A.D. often used in scholarly literature.''

Shanks told me, ''it doesn't diminish the number of canceled subscriptions we get from people on both sides of the issue, but there are authors who will not allow their work to be printed unless they determine the time demarcation used.'' Evidently many think B.C.E./C.E. is religiously neutral; others hold that the change is silly because the count remains from the birth of Jesus Christ and confuses those who think the C stands for ''Christ'' and not ''Common.''

Here's my take: I'll stick with B.C. because Christ, in American usage, refers directly to Jesus of Nazareth as if it were his last name and not a title conferring Messiah-hood. For non-Christians to knock themselves out avoiding the word Christ, when it so clearly refers to a person from whose birth we date our secular calendar's count, seems unduly strained and almost intolerant. (If you're a tiny bit uncomfortable, just drop the periods and make it BC.)

A.D. is another story. Dominus means ''lord,'' and when the lord referred to is Jesus, not God, a religious statement is made. Thus, ''the year of our Lord'' invites the query ''Whose lord?'' and we're in an argument we don't need.

Besides, if the year is not B.C., who needs a demarcation of the year? If you're writing about the birth of Jesus, write ''4 B.C.''; if you're writing about the year that B.C.E. was first used by Lady Katie Magnus, write ''1881'' without emendation.

I'm for giving John Glenn, at 75, his wish to go to the moon, provided he takes an eraser and gets to work on that plaque.