ANNIVERSARIES COME and anniversaries go, but this week marks an anniversary to which we ought to pay special attention, to say nothing of homage. The anniversary is that of the creation of the heaven and the earth; and the event was discovered - by Bishop James Ussher of Dublin (1581-1656) - to have occured at 9 a.m. on Oct. 23, 4004 BC. To be precise, Bishop Ussher said that only the earth was created on Oct. 23 (the haven having been made a day earlier). Since we know that God created different things on different days, this gives us a full week of celebrations.

Before we hear any chartling about Bishop Ussher's dating system, be assured that the good bishop was a most highly regarded churchman. In 1607 he was appointed Regius Professor of Divinity at Trinity College, and also Chancellor of St. Patrick's cathedral, Dublin. In 1621, Bishop of Meath. In 1625, Archbishop of Armagh. He was the author of 17 scholarly books, and he was buried in Westminister Abbey. It was somewhat before that (1650-54) that he wrote the "Annales Veteries et Novi Testimenti," in which he proposed the chronology that makes this week what it is.

We need not dwell on the fact that by the late 19th century Bishop Ussher's chronology had been thoroughly discredited. Suffice it to say that his views were believed a lot longer than they've been disbelieved; so you may take any side you please. To be sure, science is on the side of the scoffers. But the heaven and the earth had to be created some time; so why not six days in October?

For ourselves, we choose to go by the bishop's chronology (this week, anyway); and here's what we have to cheer about: Oct. 21: the creation of day and night. Oct. 22: the haven. Oct. 23: the earth (including "grass" and "herb yielding seed"). Oct. 24: seasons, days and years. Oct. 25: birds, whales and fish. Oct. 26: beasts, cattle, and Man (whom God was careful to distinguish from "every creeping thing"). All in all, quite a week - and that includes Friday, Oct. 27, on which God rested.

In short, this week when you say "thank God it's Friday," we urge you to sound as if you mean it.