21 Feb 2017
It is a bit counter-intuitive for programmers… but it is said right there in (the documentation)[https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators#unix_seconds]:
INT64– Returns the closest INT64 value. Halfway cases such as 1.5 or -0.5 round away from zero.
Admittedly, it might be more intuitive for non-programmers who don't know that casting in any programming language is flooring.