In the diary markets that have "continuous measurement" there are no season books, just monthly releases that cover the prior 12 weeks.BTW, would this constitute the "Spring Book?" (Or is that Spring Brook? Ahem.)
Only in markets where there are only two books or just one is there a release named after a season.
Still, I think many of use will still call the Apr-May-Jun book "Spring" anyway. And some of the industry data services like BIA show only the quarters, not the months and they use the traditional seasonal names. Maybe this is a case of "there is no wrong answer".