NH Towns That Trick or Treat on the 30th and Why?

This mystery has stumped me since I was a kid. Why does this region of The NH Seacoast traditionally trick or treat a day earlier? On October 30th? It's all about the map.

Using Google Maps and Microsoft Paint I drew a crude (very crude) outline of the cities that will have trick or treating tonight.

Portsmouth but not Kittery? Stratham, but not Newfields?

AHA!

Just to create a better jawline of what is obviously one of the most well-recognized symbols of Halloween, the skull.

I was always jealous of the kids that lived in 'night before' towns that bordered 'Halloween' towns, load up TWICE in 24 hours with little effort in the commute.

But it took me over thirty years to unravel the mystery of random (or seemingly random) locations of 'Night Before' towns.

Did the town elders of long ago create this skull shaped border on purpose?

And for those of you that think it looks more like a light bulb, that's no fun. Please let me have this NH Halloween discovery. No matter how inaccurate and irrational it may be.