I've been reading an interesting article by a sociologist (not a theologian) which mentions in passing the Scripture passage Luke 3:1-2.
The author of the article suggests that the Evangelist is employing irony by contrasting a long list of worldly powers and their juristictions with the fact that the most momentous historical event actually came to a humble "nobody" in the desert.
I always thought that St. Luke was merely placing the event in history, but I can see now that he is also possibly employing the irony the author suggests:
His observation seems to have merit - the listing "in the 15th year of the reign" should be enough to provide historical evidence to any one living in the first two centuries (the target audience of the Gospel) - but adding all that information sets up the comparison, and hence the irony.
Thanks for the post George!