This is the subject treated by Katsuhiko Sano in his graduation thesis in 2000. But, since it seems to me that his treatment was somehow prejudiced by A. N. Prior's representation of McTaggart's view, I wish to summarize McTaggart's original argument by my own reading. Each position is Earlier than some, and Later than some, of the other positions. And each position is either Past, Present, or Future.
Time involves change, and change is impossible without an A series.
In a B series without an A series, change is impossible. Each event itself is immutable, yet change must be possible with such an immutable event. Since this cannot be denied, there remains only one possibility, namely, change in time is due to the determination of the event in question by the terms of the A series. This argument shows that the A series is more fundamental than the B series, as far as time is concerned. In other words, a mere order does not determine the direction, and the A series gives that direction and hence time.