According to the A-theory, it's an objective but contingent fact about the world that it's the year 2016. What explains this contingent fact about the world? I've argued against the A-theory along these lines before, but I want to try a somewhat different tack right now. The most plausible explanation is:
- It's 2016 because a year ago it was 2015.
Which of these is (1) an example of? It doesn't seem causal. Its having been yesterday a day ago doesn't cause it to be today. Events yesterday may have caused there to be a today, but they don't cause the A-theoretic fact of its being today. It also doesn't seem to be constitutive. Its being 2016 isn't constituted by its having been 2015 a year ago. Nor does the connection between its having having been 2015 a year ago and its being 2016 now seem to be merely nomic. It's both metaphysically necessary and a priori that if it was 2015 a year ago, then it's 2016.
Of course, the A-theorist can say that (1) is an instance of a sui generis kind of explanation. But types of explanation should not be multiplied beyond necessity, and a type of explanation that applies only in one narrow set of cases seems ad hoc.