It has the very meaning.... yes, there was a change when the word UNITL was used....what? you answer that
this isn't an English sentence.
The fact is, Paul said that he had lived in good conscience with God up until that day because he had lived in good conscience with God in the days before he had been summoned before Ananias.
Clearly Paul did not believe himself to be changing on the day he went before Ananias - he was still a preacher of the Word both before and after he met with Ananias.
Likewise, St. Matthew teaches that mary had not had intercourse with with her husband in the days before Christ's conception. He does not say that she changed her behavior subsequently - that's simply a conclusion you drew and it's as valid as drawing the false conclusion that Paul was in bad conscience with God after preaching the Gospel.