I see Minecraft as its own world with its own quirks. It really isn't set in any time period, and is very broad, but if it had to be one, I'd maybe say post-apocalyptic or similar. If I had to come up with a theory on how the player's life in the world came to be, it'd be something like this:
Basically, Steve lives on an advanced planet of some sort. Soon, some catastrophic event occurs which destroyed his world. Or maybe he was exiled or something. Either way, he ended up in the world of Minecraft with next to nothing. He had only a basic knowledge of electronics, but practice improved that as Steve learned to create Pistons and such. Steve slowly finds his way in the world - an average joe having to create everything from nothing as his ancestors did, but with basic knowledge from his homeworld which accelerated his learning.