Your Warlockry:
I'm not a witch, but many of my friends are. Over the years I've noticed that, while my non-witch friends all throw their Halloween parties on Halloween Saturday, my witch friends usually throw theirs two Saturdays before.
Not that I'm complaining, mind you: double the pleasure, double the fun. Just wondering.
Clueless in Cowanistan
Dear Clueless Cowan:
There's a simple and obvious (to a witch) answer to your question, which (if you had asked them) any of your witch friends could have told you before you could count to thirteen, and it has to do with convenience and the fact that, just like everybody else, most witches hold down day jobs.
This means that, most years—ah, the times!—most witches don't actually hold their Samhain rituals on Halloween itself. The vast majority of Samhain rituals end up taking place, by default, on Halloween Saturday instead.
In short, my dear cowan: witches tend not to hold their Halloween parties on Halloween Saturday because, for many of us, that's Coven Night. Hence—witches liking a good Halloween party as much as anyone—the forward displacement.
If Boss Warlock were a different kind of warlock, he might decry what, on the face of it, might seem to be a disconnect, but in fact this Long Samhain actually has a profound theological basis. Samhain isn't just a single day on the Gregorian calendar; it's a tide of axial change in the natural year.