I don't know for sure but if I had to guess I would say late August. I usually start seeing ads in my newspaper from walgreens with some halloween stuff in it around that time. But they may put stuff on their shelves sooner. I know after Labor Day the Halloween stuff really starts to show up. After Labor Day Halloween Boutique can be found in our local mall.
I love it when Walgreens puts out there Halloween stuff. There Halloween stuff is nice and creepy.
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From my laboratory in the castle east
To the master bedroom where the vampires feast
The ghouls all came from their humble abodes
To get a jolt from my electrodes
I got a ton of stuff at walgreens after sales last year. I was still buying stuff almost a month after haloween, and there was still good stuff left for pennies on the dollar.