Luke's date for the crucifixion
Lukes superb historicity and the Prologue eyewitnesses
My reference was first simply to what we learn from the historical studies of scholars who looked closely at the history, including
William Mitchell Ramsay (1851-1939),
Colin J. Hemer (1930-1987)
Adrian Nicholas Sherwin-White (1913-1993).
Henry Joel Cadbury (1883-1974) was especially involved in the Preface studies. And even from a somewhat liberal position, he helps understand that Luke was close to the events, he also emphasizes the Luke-Acts distinctives.
The Knowledge Gained in Luke's Preface (1922)
Henry Joel Cadbury
Whether it implies an eyewitness or merely a contemporary, such a claim of intimate personal knowledge in the preface of Luke has an important bearing on the questions of date and authorship. Fifty out of the fifty-two chapters in the work go back no earlier than the fifteenth year of Tiberius Caesar. With much if not all the period from this date to the end of Acts, that is, about three decades, the author claims contemporary information. Many scholars will find here a fresh confirmation of the early date of composition recently urged by Professors A. von Hamack and C. C. Torrey.
To many who have cherished the belief that the two books to Theophilus were written by Paul’s doctor friend and associate, the suggestion will come as a welcome surprise that the preface not only may, but perhaps must, be understood to claim contemporary and first-hand knowledge. p. 417
Both parties, however, whether arguing for or against early date and Lucan authorship, will do well to eschew the conventional habits of settled exegetical conformity. Whether we believe him or not, the possibility must be left open that the author is claiming in the very beginning of his work to have been long in such close contact with the series of events which he unfolds as to be possessed of first-hand contemporary knowledge about them, and that perhaps he means to claim the knowledge of an actual eyewitness. At any rate he says nothing of research. p. 419-420
And this is even with the error of Theophilus as a Christian (p. 413). Understanding that he is the high priest of 40-41 AD simplifies the expositon.