Which of these identifies the significance of the date a. d. 597?

WHich of what? the only things that happened then is And i quote, "The Roman brand of Christianity is brought to Britain for the first time by St. Augustine, the missionary sent from Pope Gregory to convert the Saxons. Augustine lands in Kent and is welcomed by King Aethelbert whose Frankish Queen is already a Christian practicing at her church of St. Martin's, Canterbury. Augustine converts Aethelbert and his court to Christianity and founds a monastery at Canterbury. Commencement of the erection of a monastery at St. Augustine's, Canterbury, built from the Roman ruins of the old city. Death of King Ceol of Wessex. He is succeeded by his brother, Ceolwulf."

The sentence needs a descriptor of exactly "what" will happen at gurley and marina. in this case, it is the light at the intersection turning green. in this case, the sentence could be rewritten as "the light at the intersection of gurley and montezuma will turn green exactly three seconds after the light at the intersection of gurley and marina."