When does the New Years Eve hat awards?
The hat's description says "Post an upvoted question or answer on December 31."
There are a number of us who have does this and haven't been awarded this hat. Even one of our mods, RavenDreamer, is affected by this.
And yet, some people got awarded the hat correctly (See: Ashley Nunn).
The main difference appears to be that these people have had their answers accepted, but the hat description doesn't make any mention of this requirement.