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The short version: while Sonic 1's official release date was June 23rd, 1991, several Usenet posts around that time make it clear stores in various parts of the US were stocking it up to two weeks beforehand. (There's also some discussion of pre-release coverage of the game, if you're curious.)

It's an interesting look at an era of gaming where synchronized, nationwide release dates in America weren't really a thing. (As the article notes, it took quite a bit of planning to get the sequel out on "Sonic 2-sday" across the country, and even then didn't immediately become the standard.)