Actually, according to Narumi's latest dev notice, Trick-or-Treating should still be going on until midnight PST tonight.
And yet, Narumi was wrong. Halloween in Towns and Shops was turned off the midnight before. They caught their mistake only halfway today: The shopkeepers have their costumes back on, but Towns is still normal.
ToT is still going [at least for me] So it would seem that the dev alert is accurate.
But then again, I don't have a full set of the items yet.
I was far more focused on the event, so I didn't really get a chance to do ToT xD