To the people asking why not any other day? It's because Halloween creates social context as to why you are dressing up.

If you were to go out right now 9/18/16 fully dressed, the context people will think when they see you is "CDer, Tranny', Bigot's "what a faggot", some cis girls "gross", other cis girls "aw they look so cute and brave, I want their shoes", some cis guys "that's a dude right? RIGHT? idk, no it has to be"

Halloween is like "hey people are gonna be wearing weird things today, it's not some CDer, they are totally just doing this to show off their bravery to the ladies"
At least that is the context of it. To me it would feel about the same as any other day. I did however wear pink bunny ears on Easter at my job, Using the Context of the Holiday as my unspoken excuse.

If I ever get the guts and sink into the deepest pink someday, I want to try and buy Alcohol while passing as a young girl (like 18-21) It would be so funny to pass so hard that the cashier and manager can't accept your ID because the picture doesn't match. I think anyone who is trans should try this at least once in their life, Imagine how much pride you would feel knowing that you passed so well that it's not just a politically correct tolerance act...That people are completely certain that you are a girl, so certain they would rather deny alcohol than risk it on what they believe to be a girl using her BF's ID.