I have on my desk a 2017 best paper award, for a paper printed in 2016, submitted 2015, being an extended version of a 2013 paper for a problem we solved in 2012. Academic publishing is like that.
(Largely forgoing peer review as a scientific field is, however, not without problems. To say the least.)
It took us a long time (too long!) to construct that manuscript. Like SciPy itself, it was written primarily in the spare time of contributors with full time jobs. Glad to see it out there, though!